Can't get over my gf's past and I can't trust her
I have been dating my girlfriend for 3 months now. We like each other a lot. Things are going great. But the for the last 30 days, I have been stressing out and I am in a very bad mood. Here is the problem. I am 22 year old. I have only had two girls in my life. My girlfriend is 19. But she has already slept with 11 guys before me. 3 of them from her previous boyfriend which is totally fine with me. However, the rest of them 8 were from one night stands and friends with benefits. I was really grossed out by that a month ago when I asked her about her sexual past. And she told me all that. I met her at the beginning of Jan this year. She broke up with her boyfriend in last Sep, and she had a one night stand that month. And then she was having sex with her friend for a while. And this guy is ugly and he is a looser. According to her he was consoling her because she was sad and she slept with him. I want to break this guy's face if I see him.
I told her a week ago that I can't seem to get over her past. She told me that she is sorry that I can't get over it and she told me that eventually I will be able to get over it. That is why she changed and she didn't have sex for two months before we met. Yeah but she slept with me on our first date. Here is another problem, too. I am leaving for training in another city half a world away for a month. I don't think I will be able to trust her. She loves sex a lot. And most of the guys that she slept with previously are still in this same town. And I know she still talks to some of them on Facebook under private messages. Even though she told me she doesn't anymore but she is always talking to someone on Facebook, and I saw her talking to guys on Facebook also.
This girl is amazing in every other ways except for her past. I really want to get over her past and start trusting her that she won't cheat on me when I am away for training. But I can't seen to find ways to help myself. I almost wanted to cheat on her so I can feel guilty when I see her and so I can respect myself less. But I stopped myself, case I can never cheat on someone. I am constantly so worried about the relationship. I was so stressed out that I got shingles/chicken pox. Now I am even more depressed.
My question is :
1) How can I completely get over her past
2) How can I trust her when I am not around
3) Can someone really change in two months from having sex with random guys
Please help.