Your son sounds as if he has severe depression. Since he will not go back to his doctor, perhaps you can convince him to try another or to try one that you use. Most doctors are very confidential when dealing with patients, irregardless of the one who violated confidentiality. He needs to get on an antidepressant to help him elevate his mood and become a little more motivated to do something.
Perhaps, you can phone your physician and request medications for him, or take him to a hospital emergency room to assist. His depression will get worse if left untreated. Polease let me know if you have further questions.