WHATS YOUR OPINION????? CRUCIAL RELATIONSHIP QUESTION?

Me and my girlfriend have been together for the last seven months at first it was amazing, fresh and fun and I was happier in my life than I had been in along time. After the fourth month and every other week after this I have been being accused of cheating when I never did such a thing, adding to this my girlfriend has started a lot of arguments and when she feels like it threatens to dump me. Just recently I cracked and told her I wasn’t happy after suffering in silence for the last 4 weeks or more. Another problem is that after our fourth month of being together she had no where to go after her notice on her own apartment had run out so she had to come and live with me. We have had some very happy times and in the relationship at times I have felt it is right. But now I feel that I have been totally let down and been treated in a very bad way. My Girlfriend promises she will change but the accusing ruined my birthday, xmas , and I warned her that if we lived to soon it could end our relationship, I try to end it but everytime I do, she crys, and begs for another chance, I have strong feelings for her and think i am sort of in love with her and when it comes to making a descion about ending it or telling her to move out I always back down because she crys and assures me she will change, i almost feel better for knowing its over, and worried that im making a mistake, im at a loss, will she change?? should we carry on living together??? or should we have a break and see how we feel????????