<human>: Condense the text into a few key points

I want to preface this by saying, the trust issues are my fault. I have a history of being unfaithful in relationships, and am breaking the habit, by communicating, and being honest about everything that I can. In all of my past relationships, I was younger and stupid (still am), and looked for sex in other places aside from my SO, but now I am trying to mature and become the kind of person that is deserved in a relationship. 

We have been together officially for about 2 months now. The relationship is young, but I have known her for the past 6 years, being very close friends. I was up front and honest with her about my history, because I felt she deserved to know it. She, however, feels that she can't trust me. When she believes that I have been unfaithful or lied in some way, she becomes accusatory and claims that I am reverting to my old ways. I do everything I can to be honest, and open with her. We just had the worst fight we've had yet, because of her not trusting my answers to her questions.

She told me that she wishes that I would say that I understand where she is coming from and not be defensive about being accused. This is difficult for me, however, because I become defensive, instinctively, and try to keep her from believing the wrong thing, simply because I don't want her to think of me as that kind of person. I know what she wants me to do, but I'm not sure how to break my habit of being defensive and exacerbating the problem. 

Any advice would be amazing.
<bot>: My SO doesn't trust me as far as she can throw me, and I need help not being defensive in response.