as per the information provided by you and the history of Fibromyalgia
the sore mouth is the symptom of this only.
Fibromyalgia patients usually feel these symptoms as heightened pain in response to tactile pressure
of the skin and unusual pigmentation patterns on skin and mucus membranes.
you need not to worry about the mouth cancer , as per the appearance of the oral pigmentation doesn't suggest oral cancer
in your case, but you must stop smoking
as this will predispose you to oral cancer for sure .
quitting smoking will also help to return your normal sleeping pattern.