Jealousy, HELP!

So I need some advice, my boyfriend and I have been dating for a little over a year now. Am I'm madly in love. But you see I'm a very jealous person and I hate that about myself even when it comes to my girls. I don't know what to do. I'm in college and he is still in high school and he's a very popular guy and is involved in a lot of stuff so girls flock to him. I trust him full heartedly but I don't trust those girls. He is such a nice guy and sometimes can be too nice without knowing he is, so please help! I don't want to lose him because I'm being a overprotective, scared, jealous girlfriend.