Emily--I read your note in the comments here, and went and checked out your blog. Girl, I feel for you! I remember how sick and socked in the stomach I felt when I found out my X was cheating on me with a woman I considered a friend--and he was a man who swore he'd never cheat (and who, to this date, insists he didn't cheat because they didn't have intercourse till after we moved out of our house into separate apartments. Guess spending the night and being in love doesn't count).
Emily, I don't know what to say. I remember how much pain I was in and how awful it was. There is no way I can counsel you, but I would say do what is in your heart and to hell with everyone else. Take care of you and work toward the outcome you want. Express your pain and your rage and your hurt--and make sure you take care of you, first and always.
And good luck--write me if I can help in any way.