[Solved] How to help my 14 year old drug addicted son

My son is 14 and he was always a very kind boy, but has always had problems with self esteem. He would have feelings of inferiorty compared to other kids, and never had many friends. I thought it would work itself out, as he was making friends but at the end of last summer I caught him smoking weed. He said it was because it made him feel older, so we punished him severly to deter this behavior. One morning I walked past his room and the door was open, and I noticed several deep gashes on his legs, dark red and around 4 inches long and half a inch wide.