I had troubble with that for years, and did the same thing you are doing. I went to the pain clinic and after a couple of visits and shots my back felt better than it did for 20+ years, then my leg was hurting and I went back to the pain clinic and in my lower back cartaliedge (sp) was growing (due to age) and pinching the nerves in my lower back. The Dr. scraped it all away and now I am doing fine.
Ah, yes. The "Golden years"