Self confidence

I have been dating my boyfriend for over 1.5 years and we love each other very much. However, there is a very serious persistent problem in our relationship. Early in our relationship I put myself in precarious/risky situations with other guys either because I wasn't paying proper attention to the situation, or because I didn't think it was a big deal, or because I wanted to make him jealous. I never did anything physical with the guys, but the act of being so careless with my boyfriend's feelings left him very hurt. Since then, we have had many discussions about my actions, and I have agreed to change my ways and attitudes to become a better girlfriend for him. However, the act of merely becoming a good girlfriend is not enough for him to regain his self-confidence and his insecurity takes a massive toll on our relationship as we fight repetitively over the same issues. What I need to know is how does someone gain back their self-confidence after having it shaken from them in a relationship, while remaining in the same relationship with the person that caused it to be shaken in the first place? I want to help my boyfriend regain his confidence so we can move forward together but I don't know how. Please help.