> I'm a peice of shit

No, you're not. If you were just insecure, that'd be one thing. But she gave you a reason to snoop and, what's worse, now she's gaslighting you by telling you that conversation was just bait to make you snoop. No, she got caught. I 100% guarantee you she slept with that guy, and probably more than once. I know that's probably not what you want to hear but it's what you need to hear. You didn't fuck up, she did. You didn't violate the marriage, she did. As for you feeling like you're losing her, I'm sorry, but you lost her long ago. And it's most likely not anything you did. I don't know you so I'm not going to sit here and tell you you're blameless in all this, but nothing justifies cheating.

You're not a piece of shit, she is the piece of shit, and this marriage is over, but not because of you.