As far as the cause of Fibromyalgia goes, there is no official explanation: could be infection (with mycoplasma or other pathogens), stress, childhood or other trauma, spinal cord injury, thyroid problems, etc.
I would go with the rheumy, as others said. My orthopedic doctor doesn't particularly believe in fibro. He calls it polymalgia.
I even had a neurologist who didn't believe in him.
Stay with the docs that help you out.