Well, one thing is for sure, you can't control whether he uses or not. You can only control you. When he comes home, if you are pretty sure he is using (You will know it is he is) than you have two choices: stay and suffer with him, or leave and find yourself. IF he is NOT using, than you should re-examine your reasoning as to what lead you to believe he was using.
You know that old cheesy poem "If you love something, let it go. If it comes back to you, than it's yours. If it doesn't it never was yours to begin with"
Well, insert the word "clean" after the word "you", and there you go.