Don't feel guilty. You were being loving to your son. It's just that addiction is counter intuitive to everything that we understand as mothers.
I have never really heard of a true "detox" facility for meth. Meth is more of a physiological and pyschological addiction than a true physical addiction. You may exhausted and have a aches and pains but the real problem is longterm anxiety, depression, craving and disturbed sleep. There's not much that can be done for that as it's a long term effect of destroying your dopamine production abilities. You just have to get through it. It sucks. It takes time. Anti depressants might help. And face to face support. That's probably the KEY ingredient of recovery. It takes support from other addicts or counseling or god or church or whatever works.
Hopefully the detox has a follow up program because otherwise... well like I said, if he can stay clean because of it, I'm so happy for him. But mostly, try to work on you. Because no matter how much money you spend, no matter how supportive or unsupportive you are - NOTHING you do can cure his drug addiction or get him to stop using if he doesn't really really want to.
Prepare yourself and educate yourself on addiction, codependency, boundaries, recovery... read all you can on here. Ask questions. Find a support group. Alanon. Naranon. Codependent No More.
Whatever it takes.
Good luck to you.