I am no expert, but I want to say more about what I think was going on here.
I was definitely stuck in a vicious cycle, in which worrying about some part of my body caused pain in that part of the body, which caused more worry. The question is, how does this vicious cycle work? What's the mechanism? I don't know for sure, but I believe it's something like this:
Just like John Sarno says, this is not psychosomatic pain, at least not in the conventional sense of the word. It really is very painful to use your hands when there is inadequate blood flow to the muscles and nerves, etc.
So what are the factors that made me fall into this cycle? From most important to least important:
(1) There is the statement: "If I feel pain, then I should be really worried that I'm harming my body and making things worse". I believed that statement more and more and more, which obviously made me very vulnerable to fall into this vicious cycle.
(2) There is a constant stream of non-serious pain or sensations in life that can feed into the cycle: Things like everyday muscle soreness, cramps, stiffness, muscle spasms, charley horses, etc. These are a universal and harmless part of life. (Indeed, anyone who has recently started exercising knows that muscle soreness is the path to good health!) I guess I forgot about that, and overthought every pain and sensation, so I was always getting launched into the vicious cycle.
(3) There is a constant stream of psychological stressors in life which can also launch or aggrevate the vicious cycle.
There you have it! That's what I think was really happening to me in 2006-7. But you should still read Healing Back Pain.
I didn't quite make up this "vicious cycle" theory: I learned it in a very different context years later ... a class about birth pain! (They called it the "fear-tension-pain cycle".) If you know anything more about this theory (evidence for or against, or relevant literature) please let me know.