I just want to remind you Spacey, that the disease of addiction is pretty much defined by the concept of a lack of control over one's drug use. Don't beat yourself up, this is just 'what happens' to (many, many of) us when we start messing with addictive drugs. If you were somehow this unique or special case, how you're acting, what you're doing, there wouldn't be rehab centers all over the world, there'd be no AA/NA with millions and millions of members, etc, etc, etc. You are not alone, nor are you unique in regards to your actions, my friend.
This *IS* addiction, what you're doing is exactly what addicts DO, the kind of stuff all of us did in our 'using' days. Getting dope on the streets? Hell yeah most of us did that! We had the same thoughts you're describing, too, similar feelings of shame, self-loathing, all that. An abject fear of being in withdrawals? We've all been there, too.
Fact is, being an addict who's not in recovery is a miserable, depressing existence. The good news is ... being an addict in recovery, esp if you are actively working some program of recovery ... is pretty damn great
So the solution to virtually all the problems you have ... is to get clean, stay clean, and recover. Many of us here have done it (many with much more advanced addictions, I might add) so that means YOU can TOO, okay?
I'd say the time has about come for you to start reaching out for help from those around you, and start hitting some NA meetings, or something along those lines. And keep posting, kay? Good luck