My husband had an affair after we had been together for 7 years, it was a quick seemingly meaningless affair, I found out, he finished with her and begged to come back. I forgave him, it was hard but we moved on, and for 16 years it was great, then he got depressed because of a few things all building up, job pressure, child leaving home, my menopause, so turned away from him, yes, you’ve guessed it. Another affair, only I caught this one when it was in its infancy so he was totally besotted, he left me and moved in with her after a week. It obviously went tits up for him, I mean he moved in with her before they even really knew each other, or before they’d even slept together, she didn’t know about his erm, issues. They were done and over within weeks.
My point is, even after 16yrs his default in times of stress was to look for validation in someone else. If you get replies like “I don’t know why I did it” then how on earth can he stop himself from doing it again? He needs therapy to know why and to change habits, you can’t simply go back, you have to rebuild.
I’m not saying I regret those 16 years between affairs, I had some amazing times and I’ll treasure the memories I have forever, but many are tainted now and I wish he’d just let me go the first time.