It sounds like you have some history with jealousy that is interfering with this relationship. Since your new boyfriend has given you no reason to feel that he is dishonest or disloyal, the fear of losing him to another woman is in your head.
Every time you get this feeling of jealousy, slow down and don’t react. The mistake you may make is acting out on something that’s not really happening in real life –just in your head. Examine the real life situation at hand and break it down to figure out what is really happening to make you feel anxious. You’ll have to be very patient with yourself in order to do this right because it’s going to take some time.
This isn’t something you need to share with your boyfriend — work on this privately. You can talk it through here or with a girlfriend, but don’t let your personal issues become a relationship issue.