I always get jealous when he goes out with friends

I have been dating my boyfriend for four years now and I always get jealous when he goes out with friends while I'm stuck at home. I constantly watch him to see if he is staring at other girls and if he checks them out; if he does, I get so tensed up and don't want to talk for the rest of the day. He brings up our future and we aren't even in college yet. I am so afraid he is going to leave me for someone better. I want to get over my insecurities. Please help.

This question was submitted by 'alfitzwater'