I have, but it wasn't a physical (or particularly emotional) affair. He downloaded Tinder, with the intention of getting the ego boost of girls replying to his messages. He has had a sex addiction since he was a teenager but never sought support but I already knew this and naively thought it wasn't an issue. I knew that he masturbated multiple times per day, but he didn't want to seek help for this even though he'd broken down in tears to me about it in the past because of how much he hated it.
Then he came to me one evening, completely out of the blue, and handed me his phone with Tinder open. He confessed all, wanted to be honest, was in floods of tears and said he couldn't live with the guilt of knowing he'd done this and wanted to lay his cards on the table to show me that I'd been living with someone who had been unfaithful. I looked through the whole of his tinder profile, could see that he'd had two message exchanges with women (both flirty but relatively tame and not sexual in nature, no indication of meeting up or speaking outside of the app), but he had tried to message a few others with no reply. I could also see he hadn't been active for a couple of weeks before showing me but it had been going on for around 2 months before I found out.
I knew he hadn't been physically unfaithful as there was no opportunity for this to happen (won't go into detail but I know this 100%). He said that although the cravings for "more" were due to his sex addiction, he was responsible for his actions and made awful choices. He took full responsibility, but admitted that he couldn't continue in a relationship knowing that he'd sought out the "rush and thrill" of getting the attention of other women. He didn't blame me for anything, said all of the right things and to be honest I'd never seen him so devestated. He has autism and has never been great at lying or keeping secrets, he finds it very difficult and distressing, so I'm not surprised he struggled to keep it from me!
I broke up with him and he understood this. He was heartbroken, as was I, but I did not want a relationship with a sex addict who could not control his urges for "more".
Without asking me how to fix things or looking to me for direction, he took himself to the doctor to seek help. They suggested therapy but as the wait times were so long, he booked himself in the following day for a private therapy session which he attends weekly. He also went to his first Sex Addict Anonymous meeting and has attended weekly since - he has many social events and nights out with our friend group to attend these meetings instead. He phones his sponsor daily and now visits other SAA groups locally as he's found a community of people in the same boat as him, all trying to help each other.
I was very slow about considering a second chance, but in every other respect than this he was the perfect partner. Hilarious, loving, supportive, kind, gentle, we have the same hobbies and interests, he always did anything he could if he knew it would make me laugh/happy.
We have been back together now for 2 years - he has not missed an SAA meeting since then and if he can't attend in person, he attends by zoom. He continues to pay for therapy weekly, meditates, journals, does gratitude lists, reads from his SAA book daily and does his exercises to progress up the 12 steps. I've noticed a huge change in his personality, as he says that he has an addiction he would need to beat whether I'm with him or not, if he doesn't sort it now then he will live with it forever and he doesn't want to inflict that on me but also on himself. We have honest discussions and he never, ever pressured/rushed me to take him back or forgive him. He knows he is on his last chance, the slightest sniff of anything else and he's gone. I don't know what the future holds but all I can see right now is a man who made an awful decision who has done everything possible to fix, change and rectify.
He supported me through my recovery from alcohol addiction - I was gripped by the need to drink large amounts daily, but as I am now over 3 years stone cold sober I feel I should give him a chance to do what I did. He supported me, so I am supporting him. If he had progressed to a physical relationship of any nature, or even a particular emotional one where he'd had personal conversations with someone he'd developed feelings for, I don't think I could have moved past that though. If he hadn't confessed when he did, and had instead let it progress further, I wouldn't be with him today.
Does that make me an idiot? Perhaps! I have a lot of time in my life before I need to think about settling down, children etc. I'd love to spend the rest of my life with him and if he continues on the path he is now, I believe he can remain faithful. If he starts to let SAA slide, starts to show behaviours or red flags or slips back into his old ways then I will leave him and be perfectly fine on my own. I think my barriers are still up, I can't fully trust him but I can't fully trust anyone - anyone is capable of cheating, even those you least expect, but I feel that at least my DP is doing everything in his power to treat the symptoms of his addiction and remain in recovery. He wants this for himself just as much, if not more, than he wants it for me and that's the key to his success.