PleasePlease: I understand what you are saying about the worry of your son if you come clean to outsiders.
It might not be as bad as you're thinking. Does your husband come with you to your Dr. Appt's? Probably not if he doesn't know your meds or dosages. Are you being prescribed by a Dr. or buying off the street? If your Dr. is prescribing to you he must know what he is giving you - unless you are going to more than one doctor for pills.
Your Dr. (main one) if more than one, probably knows you have a 2 year old.
I suggest an appointment to discuss your drug use and to ask for help to stop taking the narcotics. If he/she knows your history it's unlikely he's going to insist on calling in CPS when he/she prescribed them for you in the first place!
Perhaps your Dr. can help with comfort measures for w/d at home. Although it would he best to be honest with your husband, if you feel you just can't but are serious about stopping the opiods, you could just have a very bad flu. If it gets too bad do you have a friend or neighbor that could babysit for you while you have this very bad flu?
You have so much to gain if you quit and so much to lose if you don't. Life with a drug addiction never gets better, it only gets worse.
We've all been through it, read and read somemore, this site has been a godsend for so many of us.
I really hope you start recovery, your baby needs you. Your husband needs you and your life needs you. (And it always worries me that someone young enough to have a 2 year old could become pregnant again!! Then what!!??
...Ruby...
As usual my warning: This is my opinion only and I may be full of it!