Maryz, I was addicted to heroin and cocaine for several years, in my early twenties. I know many, many 'recovering' addicts like myself who have got clean, and stayed clean. It really is possible.
I'm so sorry you are going through it with your son - awful for families, who are not numbed out (for the most part!) to witness and try and stay sane around.
There are supports systems in most areas for family members, as well as addicts - eg Famlies Anonymous, or AlAnon - I would strongly suggest checking them out, OP, they may well have wiser advice for you than I could possibly come up with (am too many years away from it all now to remember half the wisdom I once learnt!).
OP, I would seriously tell my beloved not to contact me until he had been to several NA, CA or AA meetings - or treatment - and had detoxed with the help of a doctor. It could be just the reality check he needs. If he can't do that, it may just not be the right time for him I'm afraid - he may need to get worse before he gets better. Very scary to watch, even from a distance, because sometimes people die instead 
MaryZ, hoping the best for you and your son, and the rest of the family...if you have never contacted Famlies Anonymous, you may find they can help support you, suggest practical ways of coping, etc.