How do I not worry about other girls?

Okay, so I have been dating my boyfriend nearly a year now. He is honestly the sweetest, and gives me absolutely NO reasons to worry. Before we started dating we were really good friends, and now we are obviously even closer. :) So basically, it is a very healthy relationship.

But I am a bit of an insecure kind of person as it is. He has boosted my self-esteem phenomenally, he makes me feel secure and happy with myself. But sometimes I can't help but compare myself to the other girls, and in my mind, they are all 10x better looking than I am.

This is also my first relationship so this kind of stuff is a bit new to me. I have never been a jealous person or anything. (I never wanted to date anyone in high school because usually those relationships don't seem to last, but he changed my mind).

I trust him, I really do. But I don't trust the girls he goes to school with (i. e.: his ex who still likes him and a few other girls that like him. He pays none of them any attention though.) they are pushy and have no respect for the fact that he is in a relationship.

I also keep having bad dreams of him leaving me for another girl. He always says I have nothing to worry about because he loves me and they are just dreams, and I believe him.

I know this is all really silly and I don't want it to cause stress or trust issues or anything in our relationship, so how do I be better at not comparing myself and not worrying?

How do I not worry about other girls?
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