Twiggy, A rheumy can diagnose fibro via a tender point test, but I believe MS would be a neurologist--you would need to get a brain MRI and spinal taps. MS is autoimmune but it is a nervous system...
Twiggy, Doctors who specialize in FMS and CFS in my experience often seem to be knowledgeable in disability claims; you could go talk to one about the pain and maybe they could help you and give you...