What to do to regain my lost love feelings and emotions?

I and my gf both are muslims and from Bangladesh.We were together for 1 year and I left her for no good reason at all. Then she found some other guy and told me about her new bf after dating for 1.5 years. I felt guilty, realized her value and wanted to be together once again. She was not happy with the other guy so she came back. But after couple of months she told me she had physical relation with the other guy but did not have . Now I'm feeling cheated cause she didn't tell me about this before. Now I can't trust her any more and beginning to imagine all sorts of nasty stuff about her and blaming her all the time. I'm going nuts because she was the kind who was crazy for me and told me she would not be with another guy ever but me. As Islam forbids a women to share her body with more than 1 guy I just can't stand her behavior. But I do love her very much and we want to get married. What can and should I do???? Will I ever be able to forget what happened. By the way 2 years more have past since she left the other guy but I remember everything she said and make her keep remembering. Plz help.