Hi Summerpeach, just another hug from someone who's been there. :ghug3
It hurts more than anything, I know. I'm glad you're using your anger to propel you forward. I pretty much crumpled into a heap on the floor and didn't move for 3 months. I encourage you to read up at Surviving Infidelity, which transformyself linked to. It will help you to understand yourself and how this happened a lot more.
I'll tell you, I have learned so much about myself. I have been cheated on by pretty much every boyfriend I've ever had. I never thought H would cheat on me. Anyway, when he did, I had to acknowledge the recurring pattern in my life and figure out what the lesson was. For me, it was an opportunity to deal with my abandonment issues.