Hi Wolverine,
I'm really sorry to hear about the situation your boyfriend is putting you through. Most non-addict people do not understand the addiction concept, which is one of the reasons I lost my wife and a whole lot friends (will-power they say is the answer to us and how wrong that is). I know it's easier said than done but you should and explain him that threats tend to work the opposite way they're intended to only because they make us feel trapped and extremely streesed even more than we already are when we first are trying to stop. That alone is the main reason why he should try and understand what you're going through. You should somehow make him see that.
As I said it's very hard for non-addict people to grasp these feelings, they may even think it's just an excuse for them to let us use. It's not if we are really willing to let go, to start any kind of rehab (NA, therapy...). You should also tell him that some kinds of pills must not be stopped cold turkey because it could be very dangerous. A doctor is in order right now.
Still, try and reason with him, see a doctor, show him you want to quit with his help, not under threats.
Love - Pedro