Relationship problem?

Im 18 and ive been going out with my girlfriend for 1 year nearly. but durning this time Sammie has dumt me 3 times for reasons she cant acount for. I trust her and I know that she didnt do it for anyone else, but she says that sometimes I tie her down. Each time she dumpt me she left me alone for a couple off week then chased me again. Each time i was doing really well in moving on but i love her that much, when she clicks her fingers I come running. Its been months since she has dumpt me and shes allways making up for it but ever since ive turned nasty with her and now im sometimes nasty to her for what she has done because Im still mad at her for hurting me so much. She says that shes truned me into a nobhead. How do I get back to my usual self, the Jon thats allways happy and nice to his girlfriend ???