Jealousy

My boyfriend is so loyal. I have no reason to be jealous of any other girls. We've been together almost a year. He worships me head to toe and I love him for it. But for some reason I still get jealous of girls talking to him for some reason. I don't know why. When we are together, he doesn't ever break eye contact to look at another girl. I think it might be because of an ex who scarred my trust? Advice?  Help!!