My first thought after reading your post was that he was doing drugs again.
However, it may be the meds that he is taking with prescription are too strong or not strong enough. So, that would be the first thing I would want him to look into. It takes a long time to get the strength correct.
I don't know about the smell though? My son's drug of choice is also meth; however, I have never smelled anything on him.
Hope it's just a matter of regulating the prescription meds, and not drugs.
Hugs, Devastated