Jeblina, understand that we can't judge him, nor are we (I) trying to.
But just try to think of this a little more rationally. You have a home now, you've been there for some time and it doesn't sound like your mom wants to pressure you out, what's waiting a few more months going to hurt? Give him more than just one months time to proove he is really done with that phase in his life. It's only going to help if you wait. Whereas if you do rush into things, move in together... and 2 months down the line he gives into temptation (he is human afterall) you're stuck with a real sticky situation... now you and most importantly, your daughter are living in the house with a drug addict.
I understand we usually put ourselves in shitty situations, but think of your daughter here - you definately don't want to put her in that situation.
I say you wait it out... see how serious he is, if he's really going to stay clean and you guys really will work out, then waiting another 6months - 1year to move in together should be no big thang.