Rehab does not always just put you on one drug to get off another, I went to rehab and was never given any drugs.
I am not saying you should go to rehab. What I am saying is that you should call a dr, annoymously if you have to and ask them the questions you are asking here, we are not doctors here and cannot ask medical questions.
I understand the fear of losing your kids I understand the fear of not using anymore and the fear of continuing to use. You are reaching out for help and that is a good thing.
How about calling your local NA hotline and asking for help.
It is pretty safe to assume that people already know you are using, we dont' hide it like we think we do.