I have that diagnosis for 20 years now, and have been researching the topic in various languages since then, and even more since we got our PC at home.
3 years ago i came upon some research results (a webmed abstract) showing a direct correlation to Vit D levels in the blood and the frequency of complaints/ symptoms among patients diagnosed with fibromylgia.
The more i delved into that, the more i found that it was also true for me. I certainly felt better in the summer and fall of every year.
Some docs here attribute "spring fever" to the depleted levels of Vitamin D by the time spring arrives.
If you can, get your Vit D level in your blood checked, if low, consult w your doc on taking D3 vitamin supplements.
Hope it helps you. (it helped me)
Despite my research, i was not aware of the gluten-free diet and its effect on fibromyalgia, but that too might play into it, afterall, if you have trouble digesting something, it is bound to affect your entire metabolism.