My b/f of two years hangs out with drug addicts. I am sick of it. Should i leave?

He says I am trying to control him and won't let him do what he wants. We had a discussion recently about hanging out with bad people, we agreed there are certain people that we bump into, like neighbors, etc. that we should have nothing to do with, the same people that he has done dope with. He won't do drugs for a few months, but then it is only a matter of time before he is hanging out with tweekers again! He thinks he should be able to do whatever he wants, including drugs at his discretion. I think if he thinks that, then he should be alone. I am sick of this whole history repeating itself bull! I leave him, he begs me back, pathetically, hunts me down even, saying that he can not stop doing dope without me and that he needs me? That happens..about every three-six months for the past two years. He just does not understand why i care so much about what he is doing, and why he can't do what he wants, whenever he wants.