I was diagnosed with fibromyalgia in 2007. I basically went to work and came home and slept. If I did any type of exercise (walking or riding a bike), I could only manage it for 30-60 minutes, then it would take me three to five days to recover from the fatigue and pain. I got very depressed and figured it would be that way the rest of my life. Then one day I was at a book store to pick a book to read on vacation, and while I was waiting for my husband, just standing around, I turned, and at my eye level, saw a book called, What Your Doctor May Not Tell You About Fibromyalgia: The Revolutionary Treatment That Can Reverse the Disease, by R. Paul St. Amand. I bought it and followed the advice in the book. In seven weeks I was completely better--no symptoms at all. It has now been five years, and I'm still well, except when I "cheat" on the diet for more than a day in a row.
Recently I discovered information about Salicylate Sensitivity, and many of the symptoms are common to SPD, so we're trying the diet for our daughter, who is 5 y.o. (called the Feingold diet). It has many of the same dietary recommendations as the fybro book, so I think there is a correlation between fybro and salicylate sensitivity, as well as contributing to SPD symptoms.
It is not for the faint of heart to do either of these diets, but I can tell you first hand that if you try it, you will feel remarkably better.