Jenna - there's more than one way to cheat...and I'm not saying that to rile you up. What I mean is that if you feel betrayed by J's OW sitch, then the cheating chapter can help. BTW, I know this from experience. I don't think my wife got down with the OM, but there is a certainly an EA. All of it is the same thing in the end.
You're fortunate. Your both young, and you have the opportunity to grow beyond something that so many of us are dealing with in our 30's and 40's. It blows, trust me. You get past this trust issue, and you are way ahead of many.