Dear birdie,
The symptoms you describe can fit any number of conditions besides Fibromyalgia and MS, including vascular and infectious diseases, autoimmune disorders such as Lupus and Rheumatoid arthritis, the number of possibilities is enormous, really. But don't let that scare you off. Get that second opinion and don't give up. You must see a neurologist for an MS consultation; Fibromyalgia is treated by a rheumatologist. People with a Fibromyalgia diagnosis can go on to develop MS or discover that they were misdiagnosed, so your concern about possible MS (and a number of other autoimmune disorders, by the way) is valid.
Testing for MS involves MRIs of the brain and spinal cord, a neurological exam that tests coordination, strength, balance and reflexes, and a lumbar puncture.
It might take some time to find the answers you seek since it is largely a process of elimination, so stick to your guns and keep bugging your doctor. Keep a symptom log and present it each time you see the doctor. When you get a specialist referral, take that log to the specialist as well and discuss it thoroughly with that doctor, too. If a doctor suggests it's in your head, that simply means they are not interested in investigating further, so go back to the drawing board and get another referral. It isn't a waste of time to get numerous tests and amble down some blind alleys, you are establishing baseline testing that may be valuable as you go along.
I know how worrisome and stressful it is when you are trying to find the answers; most everyone with a rare chronic illness has had to run the gauntlet of specialists and dead ends before they get diagnosed and finally get the treatment they need. I hope you don't have MS--but if you do, we're here to listen and answer your questions so you don't feel so alone with it.
I hope you will let us know what you find out. And while you are pursuing a diagnosis, please feel free to ask questions or vent here whenever you need to.
Kim