No. I haven't told him, and it ended. We have a don't ask, don't tell policy which we have discussed many times (we've lived in different cities for a decade, and my father cheated and left my mother, so i've always thought about how i would handle it. though, tbh, i'd made a somewhat gendered assumption that it would be him, not me).
the affair was short, it ended mutually, and I don't think there's anything to be gained from telling him, other than causing him more pain. It was entirely escapism and bad decision-making on my part, and I don't know that it would help him to know, especially as he knows the person. I don't know...I've contemplated it, because perhaps it would be easier if he was able to be angry at me, rather than sad - but I don't know. I feel like it's unloading guilt onto him and making it an easy way out of the relationship. I've discussed this endlessly with my counsellor.
but anyway, I don't want to derail your thread, because this will become about that, given general attitudes on this board. My point is, so much of what has happened in my relationship (including my infidelity but only to a point, obviously. As the other guy pointed out, it's very easy to not have sex with someone...even if the feeling is crazy-making) was to do with our lack of communication throughout the entirerity of the relationship. Even before anything happened, and I was just trying to explain how i felt, my feelings were minimised with him insisting that our relationship was perfect. It was for him. It wasn't for me. He's finally asking to go to counselling...but I feel like he's a year too late. Actually, about 8 years too late, which is when I originally wanted to go to sort out our communication difficulties.
Push him. Make him talk. It will be really hard, painful, uncomfortable, and you'll feel like you're ruining the day every time you do it. But do it. It's so much better than the alternative.