Confused

Last Tuesday I found out my fiancé had been cheating on me since we got together. It will be 2 years next month. It was with the same chick. I'm hurt and heart broken. He hasn't seen or messed with her since January. But still. How could he do this. We start Councelling next week. But I'm so back n forth on if I want to move forward or let it go. I love him so much. Idk what I should do. I talked to the girl she sent me all screenshots and everything. I'm just lost