I too have been a medical mystery since 1993. Was actually diagnosed with Systemic lupus but have a rare neuropathy that the doctor's can't seem to figure out what is going on. Just a miserable person here because they can't seem to figure out my problem.
The back though can do some really strange things though and I just recently had back surgery on 3 lower disk and may have to get 3 upper disk repaired. The surgery for me went well. My neurologist also told me that I did not need surgery on my disk and I later after suffering for two years decided to see an Orthopedic Surgeon that specializes in the back. Actually went to two. One said I did not need surgery and the other one actually took the time to further investigate it. They did a CT Mylegram on my spine and found compressed nerves. So they did the surgery. Since that surgery things improved there but I have also an auto immune disorder that is not being diagnosed and am getting eat up with nerve damage. You may want to try and see the Orthopedic back specialist and request the CT Mylegram. Your answer might be there. They did MRI's CT Scans, Labs.. same like you and found nothing. The CT Mylegram actually showed an answer! Wishing you my best!