I feel insecure in my relationship?

Ok firstly I'll start off with a little basic background to my relationship. My girlfriend and I have been together for 9 months. For the most part we've been happy together. We met through mutual friends. I will admit I'm a bit needy, and she is a bit more independent, but I think we go well together. We're both 17. She lives with her mum and sister. Her Dad is currently serving a 12 years prison sentence for murder. As well as this, when she was a child her father abused her, and her father's girlfriend tried to kill herself in front of her. She suffers from anxiety, depression, night terrors, and eating problems. Since I've been with her I've gone out of my way to be there for her to talk to, and support her etc. So basically what happened is a couple months ago I discovered her messaging her friend's boyfriend. First of all this guy is a total pervert and it made me kind of angry. She had told this guy some stuff that we had agreed not to tell anyone. It was a mistake for me to read her messages. I sat there logged onto her account and watched her talk to this guy while she said stuff like "I wonder if I'm only with him because I don't have anyone else", "I find myself wondering what it'd be like starting a new relationship", and that she's getting bored with the relationship. I was incredibly hurt by this. We kind of had a tough three weeks after that, basically breaking up. Eventually we got back together. At the time I had heard from friends that she had just gotten back together because she was lonely, and she had told me herself that she kind of regretted getting back together. However, since then things have returned to normal, and we have been going good. Even though this is true I feel incredibly insecure with her. I kind of talked to her about it and she said that she was in a bad place at the time, that she doesn't want me to think about it and that she doesn't think about it anymore. Whenever she says to me that she loves me, or something like that, or whenever I'm with her. There's a part of me that doubts her feelings for me. And I hate it. I want to talk to her about it, but I don't know what to say, or if I even should. I find myself sitting up at night thinking about it. Any advice is much appreciated.

Put the internet to work for you. via Personal Recipe 2629984