Hey Apple, Glad to meet you. It's wonderful you're learning about the disease of addiction but, if you're really serious about this guy, I think you should go to Nar anon meetings as well.
I'm an addict and alcoholic in recovery. I've lied, cheated and stole for my next high and I don't think I was different than any other addict (including your boyfriend) chasing a high. I've got no idea what your guy is up to but he's probably up to no good.
Also, have you had an AIDS test? I hope you will because it goes with the territory of IV drug users. Please take care of yourself.