I am not sure whats wrong with my girlfriend.. Please help

Soo my girlfriend and I met over some weird dating website. We hit it off immediately, went on a date and started dating afterwards. Immediately, we both felt a connection and I still do. After a couple months we were both thoroughly convinced that we were meant for eachother due to how incredibley we felt for eachother. Somewhere down the road, we both fell very deeply inlove with eachother. (please do not say that we fell inlove too early or that what we share cannot exist between teenagers. I have gotten this speech multiple times. We are both seventeen by the way.)We dated for seven months before she broke it off. When she did so, she never told me why. She kept saying that she wanted to become a new and better person and so on at first. She would also go on about how sorry she was and that she was hurting too. Then she began saying how much she missed me and began saying that she was constantly miserable without me and that she would cry herself to sleep most nights because she missed me so much and that she would have breakdowns. She would constantly say that she would always love me no matter what. We barely talked for about four months, then she called me and we began talking again. One morning she sent me a message saying that she still loved me and that she still wanted us to be together again, but wasnt sure if I wanted to. I, of course, said that I loved her too and that I would love for us to be together again. So we began dating again and for the first week we were all lovey dovey with eachother, but then she stopped. She began pushing me away when I told her i loved her or something. Today, I asked her why she had been behaving like this for the past week and she said she didnt know. I asked her if she was having second thoughts about us and she just said "yes.. no.. I dont know. You dont need to worry about it yet." This hurt, and I asked her why. She just said that she is "Scared and doesnt know why." she had mentioned before we began dating again that she was afraid of getting back together out of fear of us ending badly or her having another breakdown (which is what caused our first breakup according to her). I asked her what I could do to help or to fix this and she just said "dont let me run and hide" Which makes no sense to me since she has never hidden her feelings from me before.... When I asked how to prevent her running and hiding, she said that she didnt know. I told her I would be there for her no matter what and that she could talk to me. But honestly, I dont know how to handle this or what to do. I asked her if she needed space and she said no, and that me talking to her helped. I know for a fact that there is not another guy ivolved, so dont worry about that. I am just unsure about how to handle this because I really dont want to lose her again. I want to help her and be there for her, but I am not sure if she wants me to be. She says she does and that she loves me very much and only wants us to be together again, yet she pushes me away. Im not sure if this will help, but she is constantly putting herself down and calling herself a "whore" or a "bitch". I always do my best to convince her that she isnt, but she is a very stubborn girl. She has also mentioned before that I can do so much better, I always respond to this by saying that there is no one else in the world I would rather be with and that she is more than good enough. Does anyone have any advice as to what may be going on or how to handle this? Any help would be appreciated.

I think she has some issues with either trusting guys or she is scared to fall in love. She also sounds like she has no self confidence in herself calling herself names:( Do you know if she has had past relationships that were rough? Or if her parents got divorced? This could trigger her to start acting like this saying things like "dont let me run away" sounds like shes done it before so i suggest you sit her down and just talk about how you feel and that if she needs to tell you something that she can trust you.