AHG, I'm jealous of my BESTEST female friend and my boyfriend?

It's stupid for me to be jealous, I know. But I just can't help it. It just seems like they talk with each other A TON when they're probably not and i'm just paranoid. And whenever I get to school, they sit beside each other on the bleachers until I get there and my friend scoots over so I'm in the middle. They always talk to each other in cl instead of talking to me. And I shouldn't be jealous because she already HAS a boyfriend! lol. So how can I overcome my stupid, petty jealousy?