My Girlfriend Is Insecure and doesn't trust me?

I have been with my girl friend one years, since the start she never trusted me....I'm at Falut here, she dnt trust me cuz of my past how I was before. We went to same high school and I was class flirt, it's true that I use to flirt around alot n mess around not sleep around(still virgin) or anything you know teenager fun I was 17...we got together after graduation, I love her with all my hear, it's driving me crazy knowing that she doesn't trust me and always doubts me, and she always think that I'm going to Leave her for someone else. When I repatly told her I won't ever do that, she says %26quot;u have done it before!%26quot; I dnt flirt around I dnt talk to that many ppl she has my password to eveything, I have talk to her many times about this we fight every other week, everytime I ask her y do u think about me that way she always thinking bad of me like I'm doing something bad, she says she can't help it what her mind thinks. She don't open up to me she goes n open to her friend which is a guy she knows il dnt like that. She my best friend my homie my eveything. I always wann see her but sometime she can't I always call her when I get to work I work night shift. Last night she says this to me %26quot; Cuz you always complain about me and when you find this one girl who really understands you and you feel really happy with her then your mind is going to change...you can talk easily with ppl and your okay with your life changing but I am not like that...so it would be easier for you to move on compare to me%26quot; when i asked her y do u think I will leave you? Only complain I have that she don't trust me, she also gets mad when I talk to a girl not like I'm flirting with me girls I talk to have bf or older then me or my boyz girl...I would say stuff like can't say hi...ur pretty...forgot me....is not like i do that everyday to random girl, to ppl I know. She does that same. When I ask her she only joking, she treats me like crap but I still love her. She also say indnt regrade my past. I told her if I didn't y m I hurt or get mad. She saying that I need to stop making big deals outta dis, I told her I'm not I need to clear everything out. Leaving me at point that ibwann take a brake but it will just mess the relationship up? What should I do?My Girlfriend Is Insecure and doesn't trust me?you need to think about where this relationship is going if there isn't any trust on her part.. she's telling you to not make such a big deal out of it.. well doesn't she realize that a relationship WILL NEVER WORK if there isn't trust! She has NO right to keep bringing up your past.. she can't change it and the more she thinks about it the worse the situation will get.. you need to sit her down and ask her if you can have a fresh new start never bringing up the past tell her its you and her now and no one else and if that isn't good enough for her then she isn't good enough for you.. i don't think she realizes what she has with you.. she's lucky to have a guy like you. I hope it works out for you but if she can't forget the past, it's only going to get worse.. trust me.