T.F.
Having worked with addicts, your boyfriend's excuses are pretty typical of an addict not wanting to quit. Most people who struggle with addiction have to quit several times before it sticks; and many addicts really have to "hit bottom" -- and lose things that are dear to them, like relationships, jobs, etc -- before they are ready to really commit to making a change and getting clean. If you do not follow through with what you said you would do -- leave him if he doesn't get clean -- you will be effectively enabling his drug use. It is hard to let go of a relationship, but I encourage you to stay strong, for both of your sakes. Please know, too, that organizations like NA and AA can be really wonderful supports for people in recovery, and are not "preying on others weaknesses"; they are run by fellow recovering addicts and not by somebody trying to make money off of suffering. I always encourage people to check out several different meeting times and locations to find a "home group" that they feel comfortable with. You can look in the yellow pages for Alcoholics Anonymous, or do an online search, and you will find the meeting times and locations in your area. There are generally TONS of meetings to choose from, depending on where you live.
Good luck!!