I'm jealous of his ex- help!?

I'm jealous of my boyfriend's relationship with his ex. She was his first love, and I'm so pathetically jealous of it! We still have issues about her all the time. He says he's completely over her, but I'm not so sure. I mean, he did try to get her back for almost a year while we were dating! We broke up and then got back together. Please give me some ways to get over being so stupidly jealous!