You certainly are having a lot of pain. I'm so sorry. Let me try to answer your question and give you a few things to read.
First off, it is completely possible to have both multiple sclerosis and fibromyalgia. There is a MS message board which I used to read that had members diagnosed with both MS and FM. Some of the medications used for pain (anti-seizure meds) in one are also used in the other.
Please keep in mind that I have MS and do not have fibromyalgia (although my mother does). For a nice description of FM, check out this article at the Mayo Clinic which does include the description of wide-spread pain, as do you. Fatigue, depression, dizziness are also included.
The NIH MedlinePlus website has links to lots of really great information about fibromyalgia., including this news article which describes abnormalities seen in the brain scans of women who have FM.
A rheumatologist is the appropriate doctor to consult for diagnosing and treating fibromyalgia. There is no single diagnostic test to determine FM, but other diseases which might cause the same symptoms must be eliminated, such as multiple sclerosis.
A neurologist is the appropriate doctor to consult for diagnosing and treating MS, preferably a neurologist who specializes in MS. Again, there is no single diagnostic test and it's a process of elimination. Even MS is not the only cause for "white spots" to appear in a brain MRI, some lesions can develop as we age.
In diagnosing MS, there are generally the following tests needed: blood tests to eliminate other causes of symptoms (such as Lyme disease, B12 deficiency, etc.); MRI scan of the brain (and c-spine if suspected) performed with and without a contrast agent injected into a vein; evoked potentials; and lumbar puncture to test cerebral spinal fluid (also called spinal tap).
Have you seen a neurologist or rheumatologist? Have you undergone each of the tests mentioned above?
To my layman's ears, swelling of joints can accompany fibromyalgia, rheumatoid arthritis (which I am as well), lupus, and other rheumatological diseases. Symptoms of MS can include the odd sensations and pain you describe (parathesias and dysesthesias), but they can also be seen in FM as well as Lyme disease.
Also, with MS, evidence of demyelination needs to be proven to be separated by time and location. Were you diagnosed with "probable/possible MS"? If so, then you are living in limbo until further developments. The National MS Society (US) has quite a bit of information which you may find useful.
I'm sorry that I probably haven't helped you much, but hopefully you will find the information in the links to be helpful. Thank you for your question.