Cheater

So Hillary has been cheating on me with her ex boyfriend. She cheated on me "five times" between "February, 2010 and July, 2010."

I am absolutely devastated. I thought she was the love of me life, I thought I would marry her. She is my first real love, and I still love and care about her so deeply. She says she loves and cares about me, too, and that her cheating "wasn't a personal attack on" me but that she was "confused" and didn't think she was "gay enough" for me. But how can someone cheat when they truly love and care about the person they are in a relationship with? Why couldn't she talk to me about how she was feeling instead of sleeping with her ex?

She always told me not to worry about him. He was her first love, the only guy she ever really enjoyed sleeping with, but he never had an interest in her after he broke her heart in high school, and she pined after him like a lost puppy. They were "just good friends" who talked frequently enough. I never met him, she wouldn't allow me to meet him, even though she talked about him enough. So last night she told me that they have been fucking, for lack of a better expression, in our bed, in our apartment.

I am completely at a loss. I had every opportunity to cheat on her, when I was abroad and when I was home, and I never did. AND an ex is an ex for a reason, as I say, and once that drama is over it's over for good.

I haven't slept in over 30 hours and I haven't eaten anything. There was a period of time that I couldn't stop crying. I just kept saying "no, no, no, tell me you're lying." It brought back so many different memories. It reminded me of when my father died, losing a huge piece of myself that would never be replaced. It reminded me of when I was 14 and I was sexually assaulted and I lost my innocence. I was totally violated, and this situation makes me feel dirty, violated and wrong.

Just last Saturday she was holding my hand at a party, trying to pull me into the bathroom with her. She didn't seem too confused then. Why has she been stringing me along all these months just to devastate me now? What if we had gotten married and I learned the truth too late?

She wants my forgiveness, she wants to try and rebuild this relationship and repair my heart. I don't know if I will be able to do that. I am so enraged right now, and so depressed, and so lost. I love her and care about her, but I am entirely unsure as to what to do.

Any advice?