worried about my 2nd born

My highly functioning alcoholic 21 year old son is starting to show signs and cannot hide his abuse.  He's been staying over night quite a bit here and there at various friends' houses.  Last Wednesday night he texted me and told me that he drank too much.  He finished his paper and went to visit his gf's place of employment - a restaurant bar.  I knew what would happen.  Last time I talked to her about him she said that he was doing "better" because he was shaking or sweating anymore.  I knew that he had tried to stop awhile back and that  was when he had the shakes.  Obviously, he's drinking.  Darn.  Just when life seemed to be finally coming together for him ~ straight A's, maturity, happy, great girlfriend........ sigh...