<human>: My girlfriend and I have been together for 13 months, close to about 18 months ago I slept with my sisters friend, twice, it was shit, before I even knew my current girlfriend. I met her,** insert romantic story** and things went perfectly, soon after I told her what I had done and she was funny about it but was expected. Fast forward a few months in, we have special time for the first time, all played by her rules ( timing, where and when sort of stuff, she was a virgin and I wanted to be respectful to her) and things were pretty good! She had flares of insecurities about my past , regret, but we soldier on. My issue now is that things are getting progressively worse, she thinks about that situation very often which in turn makes her angry, at me. I try to keep my cool but when the person you want to spend the rest of your life with is hurting because of you mistake it gets to you! We fight every so often but it's always over this, she won't accept halo and I've done all I feel I can, what advice can you give me to help improve/ lessen her pain! Breaking up is bit an option, EVER!!

Summarize the given text in a few sentences.
<bot>: Girlfriend of 13 months hates the fact I slept with someone else before her, she was Virgin, I want to marry her! Suggestions?