I have had many symptoms like you and just recently found I had Arachnoiditis......have you (like so many of us back pain sufferers) had any steroid epidurals/myelograms/or any kind of lumbar punctures/trama (the most common causes of this codition) ?? My numbness is constant in some areas and travels in others....might be worth a look to see if you have any other of the symptoms. I will warn you though, docs don't like to give the Dx since its so hard to prove. Anyway here is a link if you want to check it out.
http://p102.ezboard.com/barachnoiditissupport