I tell myself the same things sometimes, "Why does it matter?" I try to remember that it was during our break. And it was just a break, I was going through a lot and just couldn't and didn't want to handle anything anymore.
My logical side, is like what does it matter what he did, we weren't together, it shouldn't affect me, because he was doing his own thing. But it still affects me even though I try to think of it logically, my mind just goes crazy.

However, when we were back together, I had the phone call from the ex-coworker saying they were still being intimate and what had happened when we weren't together. And she tried real hard to get him back or take revenge or something, I'm not really sure what.

My previous relationships where I've caught infidelity, I ended asap, this is the only relationship where I still want to be with the person and I didn't end it. This is also the first time I actually believe the guy of having no sexual encounter. (other things may have happened though)