Hon, I managed to get over a 10 year marriage after he'd cheated for the 3rd time and left to be with her - if I can do it, so can you.
I'm not saying it's easy, because it's not and I struggled to cope for a long time.
You just have to keep yourself and your mind busy and occupied at all times. Surround yourself with family, friends, get new hobbies, go to the gym, talk about it and get it off your chest (you have these forums to talk and vent whenever you want)....do ANYTHING and so that you are not just sitting at home dwelling on it. If you just sit around thinking about her and what she did, you will drive yourself crazy and may end up doing something you regret. And she isn't worth being arrested for or the time you might do.
So how did you find out then? More likely because she came back, been feeling guilty about what she did and was distant? That is usually the first sign something is wrong.