Re: I dont know what to do .....
For this to get to the point it's at right now makes me think that you guys didn't put anywhere near enough work into things the first time. Have you both read Not Just Friends by Shirley Glass? If not, get it RIGHT NOW and read it.
You should be able to tell him that what he is doing is unacceptable and he should accept that it is, as a direct result of what HE did a few years ago. THIS IS THE NEW REALITY after you've cheated. You DO NOT GET to be 'buddies' with an opposite sex co worker. The fact he thinks he can tells me he isn't remorseful for what he did the first time around. And if it is all in fact innocent, he should be BENDING OVER BACKWARDS to help you feel better about the whole thing.
If I were you I wouldn't even bother to gather any more evidence. I would tell him straight up that this is a dealbreaker for you. He CAN NOT act this way, EVER, and if he doesn't agree it's D time.
I know that, in my own life, right now, 7 years into R with a truly remorseful husband, if I told him, EVEN TODAY, that I was uncomfortable with a relationship he had with a woman - whatever woman, coworker, hairdresser, WHOEVER - he would do everything within his power to set my mind at ease. He wouldn't get mad or accuse me of not trusting him or try to just convince me it was all innocent. None of that would fly and he knows it.
People don't get a free pass to cheat just because their marriage sucks. Our R