How should i tell him? i don't wanna be a control freak.?

i hate it when my bf he hangs out/around with other girls. he's the kinda charming type of person, so i'm kinda worried. i just get like, frigging annoyed. especially when he hangs out with this girl, we'll just call her mary. well, mary used to like him, and he found out through a friend. and a while after he heard about he, he thought about her for a while. and i just really hate mary now. not because of she liking him, but she's just, a b****. i've told him that i don't like him hanging around other girls. but he doesn't really seem to change. and i wanna just tell him straight, about how i don't like it, especially when he hangs out/around with mary. i don't want to sound like a control freak or anything so.. help, please..