When Can I Trust Again?

Today, 2 months ago I gave my B/f an ultimatum, Me or your O/C's you cannot have both because I cannot live this way. I spent the last of 6 months feeling so low and not knowing why (he avoided me but hung on to me through phone and manipulation). We have 5 yrs and a bit together. I do love him very much but I feel like he could do it again and I am constantly looking for signs of him using. I check his phones (house and cell) caller ID. I question him about who he has seen or heard from today.

2 months ago he had decided he had to stop what he was doing, For years he had been doing percocets, then for 8 months he was on oxycontins. He was severely depressed because he felt he could not live without his pills(o/c's) about 10 to 15 a day @ 80 mils. He went to dealer and bought enough for a couple days and told her he was going to disappear and go climb some walls somewhere before he completely lost everything.(me included). She stepped in and told him he would die or kill himself if he did it that way. She brought him to her house to wean off. When ifound out about this i wasn't to happy in the least, but was willing to try it (but didn't know she was his dealer till a week or so later),
he told me. This seemed to go on for too long and they were telling me he was down to two a day and pretty much ready to quit, i found out differently because I overheard a a conversation they were having regarding me (she was tellling him to tell me to f#*k off because iwas rushing the situation and didn't know what the f*# k I was talking about) I overheard this conversation via his cellphone, he had inavertently dialled my number while he was there getting his fix and she was tellin him that " oh _____ why are you taking this you just had one an hour ago?" I felt like i was dying as i listened to him snort his oxy. That was it for me. I phoned her and let her know exactly what i think of her and he phoned me begging for one more chance and a chance to go away with me to do this the way i wanted to. I had done alot of research and knew they were just stalling so that she could continue making $$$ off of him an dhe could continue getting stoned. One of the conditions i had set for this to happen was that the dealer/friend is history, and i never wanted her to darken my path or his doorway again.

That was a month ago, he has been clean now for a whole month. But over the march break i have been staying at his house with him and while he was out getting groceries, she shows up at his door supposedly bringing him her empty popcans for recycling(BS), then she looked so surprised to see me there and withouit missing a beat starts to greet me like i was her damn long lost friend. I put up my hands to to let her know (GET OUT OF MY FACE!!!!!), and turned my back to her and went down to the basement. I phoned him on his cell to let him know she had come by and how upset i was, he seemed genuinely upset too, because he swears he told her that he had to discontinue their friendship to stop using and also was one of my conditions for me to continue being with him. But i am so confused by all this I mean there are not much changes in him yet, and he should have made some progress toward normalcy by now shouldn't he have?
He does have more energy but not a lot. He is not weepy anymore. I just don't know if i could trust him again, because he complettely snowballed me for the whole time we have been together, I did find out about about the perks but believed him when he told me he had stopped them after the one time he lost count (due to complete depression) and overdosed himself and ended up in the hospital. I really just don't understand, is he playing me for a fool or is he being honest with me?
Has he been to rehab or any AA/NA meetings or to a counselor or anything? I hate to say this, but if he is just trying to quit on his own, the chances are not good. He needs the support of other addicts and a sponsor or something like that in order to stay clean. As far as the girl goes, she probably was coming by to "test the water" so to speak and check to see if he was actually off the drugs. She probably wanted to sell him something, too, since she is missing the money she made off him.
As far as you go, what you decide is up to you. You can still love him, but if you are suspicious, then he may still be using. The only thing that is going to calm your fears is if he is really serious about quitting, then he will at least go to meetings. But, he has to want to. You can't threaten him with it, but you can suggest it. Tell him you have been talking on this web site and there is good advice on here if he wants to look at it.

Good luck to you!!