Hi Dear, jealousy is very common problem in relationship. But if it is beyond your control then becomes problem. If you are still in relationship with that person then try to talj with him about your insecurities, dont doubt but share your feelings in positive attitude. Also you try to find out reason behind your insecurities. As you mentioned that he proved your doubt wrong then why you still feel same. I'm sure you must be frustrated by regular fights on same topic. But you can overcome this.