One of the problems that many people with fibromyalgia face is that there are no tests that definitively show that you have fibromyalgia. However, what scientists have learned quite a bit about what causes fibromyalgia what goes wrong to create whole body pain. There are some genetic factors that have been shown to be related to a higher risk of getting fibromyalgia. In addition, stress can be a factor, including physical, like car accident, viral infections, repeated intense emotional stress, and other autoimmune disorders.
It is clear that there is too much activity in the nervous system, and the whole central nervous system becomes hypersensitive. Brain scans of people with fibromyalgia and examination of spinal fluid have shown that fibromyalgia is a real thing, not something that is "just in your head."
Dadabhoy D, Clauw D. therapy in sight: fibromyalgia-different type of pain needing a different type of treatment. Nature clinical practice rheumatology posted 07/12/2006.