Taking a gulp of red wine, my hands hover over my laptop.For three weeks I’ve desperately fought the urge to log in to my husband’s email account and click on a message I’d spotted, the one with the unsettling subject line ‘What a beautiful woman’.Now, taking a deep breath, I furiously type in the password, close my eyes and hit enter.At 47, I’m about to get confirmation that my charming, charismatic, passionate husband Gianni has been cheating on me.Yet while there is a well-trodden emotional path for betrayed wives – devastation, anger, hurt – my situation is rather more complicated. Because there is no guidance for a woman, like me, whose husband is in hospital dying from a brain tumour.Do I leave a man who, I will learn, has so little respect for me that he has been unfaithful multiple times?Or do I feel that it would be too cruel to abandon Gianni now, when I have vowed to love him in sickness and in health?Am I trapped by his terminal illness into staying – or free to go with whatever feels right because he will be leaving this world shortly? Kerstin Pilz with her husband, Gianni. She met the Italian three years after getting a divorce Their relationship evolved rapidly, but Kerstin eventually discovered he had cheated on herIt’s an emotional maelstrom, and the contrast to the sheer joy I felt when we met could not be more stark.The moment I’d locked eyes with Gianni four years earlier I’d been instantly intrigued by this well-dressed Italian, a retired forensic psychologist 13 years my senior.We’d met at the launch of a book I’d written on the works of an Italian novelist – I’m head of Italian studies at a university – and he’d come along because of the connection with his home country.On our first two dates we talked about our lives and families. Gianni told me about his two adult children and his previous relationships.I opened up about my divorce three years earlier and how I’d been denied the chance of motherhood because of a medical complication. I spared nothing – and I thought he’d done the same.The chemistry was electric and three weeks later I was in Gianni’s bed, experiencing a passion unlike anything I’d known before.After just three months I moved into his apartment, not caring that I was throwing caution to the wind.As we took walks on the beach and watched the moon rise, it seemed too good to be true. But after the years I’d been through I felt I was owed some uncomplicated joy. The situation was complicated by the retired forensic psychologist suffering from melanoma The skin cancer, which was discovered from a mark on his head, soon spread to Gianni's brainBeing with Gianni made me feel adventurous, and I signed up to lecture on a four-month long study cruise run by a group of universities. He would come with me.Then, weeks before we were due to set sail, I spotted a strangely shaped mark on Gianni’s head.It turned out to be melanoma – skin cancer – but thankfully we’d caught it early. ‘You saved my life,’ Gianni said as he showered me with kisses, compliments and gifts.By the time we boarded the ship I realised that Gianni flirted with anyone and everyone. But it was a fundamental part of who he was and it didn’t worry me.And when, two months into our voyage, Gianni proposed, I said ‘yes’ without hesitation.One month later we said our vows in a ceremony on board the ship.That night, after we collapsed into bed, I was a little surprised when Gianni reached for his laptop, even more at the long message he was writing. But when he explained that he wanted to share our news, I understood.After our voyage finished we decided to go to Italy to see Gianni’s family in Sardinia.He said he also needed to sort out identity documents and would disappear for hours to go to the local government offices.Knowing how complicated Italian bureaucracy was, I didn’t question it, or the fact he then apparently needed to travel to Rome to get it done.And when Gianni told me he needed to stay in Italy for another two weeks to help his mother move house, while I flew back to Australia – where we were living – I just thought he was being a good son.After we were reunited, we began planning our next adventure.Then he found a small lump behind his ear. Devastatingly, a scan eventually revealed that the original melanoma had spread. It was treatable but not curable.Gianni was forever on his computer and phone, and I tried to give him space to manage his anxiety as he saw best, especially as he needed surgery on both his neck and his lungs.Our happy newlywed bubble suddenly felt like a lifetime ago.We decided to have a second wedding to legally cement the vows we’d made on the ship.The months that followed were hard, with Gianni struggling with his treatments and suddenly flaring into anger.I tried to care for him as best I could, endlessly researching the best anti-cancer foods and then cooking them for him, taking the role of a nurse, showering him and helping him use the toilet.Then – a year later – came the truly awful news that the cancer had spread to Gianni’s brain and he needed urgent surgery.It was at this point he needed to find some medical records, which were all in his email. Frantic, but too ill to access them himself, Gianni gave me his password.After quickly finding the documents he needed I was about to log out when I spotted an email from someone called Irma, with the subject title ‘Che Bella donna’. It meant ‘What a beautiful woman.’‘The sender must mean me,’ I thought in confusion. ‘But I’ve never heard of Irma.’I didn’t click on it. But three weeks later – the night before I was due to collect Gianni from hospital after his brain surgery – with a nagging sense that I had to know more, I logged in again.With my heart thumping I saw that the email had been sent when Gianni was in Rome supposedly getting his identity card renewed two years before.Opening it, I read: ‘So happy to finally have met Fabienne. You’re the perfect couple.’I’d heard of Fabienne – Gianni told me about her when we first me. She was an Italian woman he’d previously had a relationship with but he said it hadn’t worked out, and that she was heartbroken when it ended.And yet, searching her name produced pages of emails – the most recent sent just three days before. They’d maintained their connection the entire time Gianni and I had been together.These were not emails between platonic friends either; I read about exploding orgasms and seductive kisses.In horror, I realised that Gianni had even written to her from the honeymoon suite on our wedding night. He’d lied to me; he hadn’t been emailing his family, but his lover.I felt sick.In a trance I kept scrolling and realised she wasn’t the only woman Gianni had been sending sexual emails to.There was Antonella, a schoolteacher from Rome, and someone called Stefania. With a stomach-dropping jolt I realised she was someone I’d met on our visits to Sardinia.I remember her welcoming us both into her house for dinner. She was Gianni’s age. The idea she’d been having an affair with Gianni and had pretended to be my friend was too much.I didn’t know how long he’d been seeing Antonella and Stefania, but it was clear these romances pre-dated me. I have no idea if they knew about each other.The sexual fantasies in these emails hurt, but the loving intimacies were even worse. Seeing Gianni’s sweet ‘good mornings’ and caring ‘good nights’, the little Italian phrases he used with me said to other women, cut deep.There were other hurts. Fabienne had criticised the way I’d been taking care of him and he didn’t defend me. After everything I’d done for him as he struggled!Unable to bear it any longer, I slammed the laptop shut.Many women, faced with this staggering betrayal, would simply pack their bags and leave.Part of me wanted to do this.So why did I stay? For so many complicated, painful reasons. First, I loved him, despite everything he’d done.And I knew what loneliness was; before Gianni, I’d been a woman married to her job and didn’t want to go back there.Then there was the undeniable fact that he was being punished so horribly by the universe already. I didn’t want to be the kind of woman to give a dying man even more pain. I wanted to be a better, bigger person. I didn’t want to be someone who closed their heart and became bitter.Still, it was hard. The next morning, I walked into Gianni’s hospital room, ready to take him home. ‘You’re a lucky woman, I hope you know that,’ the nurse told me with a smile. I had to stop myself from telling her everything this ‘charming man’ had done.I felt ill when Gianni, his face lighting up as he saw me, told me he loved me.On autopilot I helped him into the shower, something I’d always done instead of the nurses to preserve his dignity. Now I felt an almost uncontrolled fury.‘I’m good enough for you when you can’t even wash yourself,’ I thought. ‘Then in the good times you just run off to have sex with these women.’Unable to face confronting him in person, a few hours after we got home, I handed him a letter in which I told him I knew about his infidelities.Yet if I thought he would admit everything and beg for forgiveness I was wrong.‘If you’d been different, I wouldn’t have had to see other women,’ he told me cruelly. ‘How can you have done this to me when I am at my most vulnerable?’I walked away thinking, ‘You don’t deserve me. You don’t even understand what I’m giving you here.’But still I stuck to the decision I’d made.Despite my heartbreak I did my best to be supportive and kind.Love was the emotion that determined how I acted – not the negativity of anger and resentment.He never explained why he had married me if he had no intention of ending it with his lovers – and I never asked, not seeing the point in adding to my pain.But over time I could see in his looks and the way he took my hand that he was grateful for what I was doing. As he became sicker, those feelings only grew.‘I know it’s not easy for you and I accept that I made you suffer,’ Gianni said to me quietly one day. It was the closest he came to an apology and I accepted that.In the end we had eight months together after his brain surgery.In his final few weeks my anger vanished completely.Staring death in the face together made it an intimate, unexpectedly beautiful time.It gave us both a sense of closure and made me realise how right I’d been to stay. I was by his side when he died on January 1, 2011, five-and-a-half years after we met.I still had unfinished business, however – his lovers. They’d known he was ill and I decided they should be told about his passing.So, at 2am the day before Gianni’s funeral I reached for the phone and, on the other side of the world, a woman answered.It was Antonella in Rome, the teacher who’d been sleeping with Gianni. As I explained who I was, and that Gianni had died, I could hear the shock in her voice. ‘I know he meant a lot to you,’ I said.Next, I called Fabienne and left a voicemail. Five minutes later she texted back: ‘Thank you from the bottom of my heart for offering your forgiveness.’I felt a wave of relief as a burden was released from inside me. I felt seen and acknowledged by women who had also loved Gianni.I didn’t call Stefania. I just couldn’t bring myself to speak to the woman who’d pretended to be my friend while sleeping with my husband.Grief is always painful, doubly so if the person who’s gone betrayed you.Despite forgiving Gianni, trusting men again was hard. A fling with a younger man a year after Gianni’s death quickly fizzled out, but four months after that I met an amazing man who is still my partner.People ask if I regret meeting Gianni – or standing by him later. My answer is ‘no’.Our love will always be a part of me, just like the pain and heartbreak he put me through.It showed me both the power of forgiveness, and just how strong I really am.Irma, Fabienne, Antonella and Stefania’s names have been changed.Loving My lying, dying, cheating husband: A Memoir of a whirlwind romance gone wrong, by Kerstin Pilz (£9.95) is on sale now.As told to KATE GRAHAM