MG,
I am so sorry to hear about the pain you are experiencing. You are such a wonderful and caring person. I am very fortunate in that I have not had to experience that with my son. He is 26, and as of yet has not tried drugs. If he was an addict, I know it would break my heart, and I would probably have many sleepless nights.
I don't know which must be harder for you, hearing from him and knowing what he is doing, having him express bad feelings for you, or not hearing from him and wondering if he is allright.
I don't know if it's possible for you to find any peace in this situation, but you and your son have my prayers. I do believe in the power of prayer.
Juls