kat,
I lived with my ex too...and after two years, after "relapse" after "relapse" (really just spread apart using) I locked him out after the last one, and then asked him to pack his things.
I still love the good half of that man, and probably always will, I just simply could NOT stand having crack (and all of the behaviors that go with it, and I probably don't even know the half of it!!) in my life anymore. I couldn't have him without the crack because for whatever reason he couldn't/wouldn't really be done with it.
Over those two years I worked really hard, at my own sobriety, at his, and at my own codependency. This means that my way of "helping" kept morphing into more detached, healthier ways of interacting. I think letting him go this last time was the healthiest thing I could have possibly done...for him and for me.
I don't know what will happen in the future. All I know was that the using/reacting; addiction/despair; lies/intuition/fear/blame/shame/hurt/deceit/etc etc etc., wasn't working and was unhealthy for both of us. It has been 5 weeks since I said "no more" and every day gets lighter, brighter, better understanding, and better compassion for him too.
My advice? You can only know what you know when you know it. Instead of trying to "help" him you can put that effort into understanding yourself, read everything here, talk to people, keep loving yourself...and start to learn to trust: yourself.