Ok... Just a little bit of info as to how I found out about it (which was today, by the way).
So, we were making out in my car like we've been doing before, but things got a bit heavier. My hand went down to her pants and blah blah blah. She said 'not under the pants'. I complied, like the excellent boyfriend I am (well look at me being all egotistical). About twenty minutes later she said 'so I suppose you're wondering why I didn't want you to do that.' I told her 'well, kinda'. She then explained to me how she's not actually a virgin, but she's had sex only once before -- she was raped. By a family member.
And on top of all that, her father was an abusive alcoholic.
So, what do I do?
I don't know how I can make her see that there aren't JUST bad people in the world. I don't know how I can make it better, and when I was trying to talk all I could say was 'i'm so sorry' over and over again. maybe I was a bit overwhelmed?