I feel for you. I have a 19 year old sa. I could tell a lot of horror stories. I think the best thing I can do Is to share what I wish I could have done differently. I truly tried every possible thing ... Except Detaching. I wish I had done that sooner.
As long as my son knew I would be there to clean up his every crisis he knew he had nothing to worry about. He now knows I will not be there to cushion his fall and for the first time in his life he seems to be taking responsibility for his actions. Unfortunately he's in jail... But his phone calls are to thank me, to let me know he's looking for a program for when he gets out, to say he loves me. I hope this isn't just jailhouse talk, but if it is that's for him to deal with. Tonight he started complaining a bit I told him that all I could do for him is love him and pray for him, everything else is up to him... The course of his life is up to him.
I know as a mom you want to save your son. The best thing you can do for him is to hold him accountable for his actions. Set firm boundaries and follow through on any consequences you set. Loving an addict requires a completely different set of tools than you ever thought you would need with a non-addicted child. Keep going to meetings and learn as much as you can. There is hope for your child, but, more importantly, there is hope for YOU!