Hi!
I'm sorry your son is having such a rough time. His denial is just another symptom of the depression. I admire your courage and what you are doing for your son. You see, I lost my 23 year old son to depression 10 years ago. He was an expert at hiding it from me and most others. But instead of letting me help once I found out what was going on he had already decided that living was too painful and ended it all.
The reason I'm sharing this is to help you know something you already are aware of...that what he's suffering is very real and can have horrific consequences. Even if he pushes you away, don't give up. He's counting on you being there even if he won't take your suggestions. I guess if I were in your shoes I'd force the issue of getting help and might even force him to go for inpatient care. I wish I had known sooner with my son and had a chance to step in and at least try. Do whatever you can even if you fear he won't love you afterwords.
As far as help in the Pittsburgh area (answering your other post here)...I'm in Washington state and hubby was born and spend his first 10 years just outside of Pittsburgh. But that was ages ago. One thing you might try is a university/teaching hospital. There you get the most advanced and current treatments. In your area there are several you could try. Just give them a call and let them know what kind of help you are looking for. In the Chronic Pain 101 thread at the top of the listings, there is a link for university hospitals around the workd. Hope this helps...
en.wikipedia.org/wiki/List_of_university_hospitalsChutz