I don't know how or why he told you? Did you get circumstances (was he drunk and you weren't there, did he seek her out, was it recently or last year, etc., what happened?)?

I would get to talking with him, not about whether you can trust him or he should be "punished"/have consequences for what he did (in the past now) but about your all's relationship; obviously what you think/feel is not what he is thinking/feeling?

It is hard for me to imagine my getting bored/straying from my husband because we talk so well together and are almost in each other's hip pocket knowing what the other is doing, if they aren't doing it with us. I am friends with my husband's ex- (and she visits our house each year for Mother's Day and we often celebrate joint holidays together, etc.) and his friends are mine and mine, he knows.

Don't get me wrong; I have my own life and interests and he has his! But we are interested in each other's lives and listening to each other talk about those lives and experiences and getting the other's point of view and explaining the jokes, etc.

I met my husband at work but he and his ex-wife had no communication in their marriage is how my husband and I got together. When he told her he was unhappy and moving out (and why), she went and changed her hair style to try and make herself more attractive to him; that was her understanding of how to keep a man :-) The understanding of communication and deeper issues just was not there for her.