hi i had gone through your query and understand your concerns. i would come up with two possibilities
1.the first one include;ACID PEPTIC DISEASE
-the medicines taking for fibromyalgia
may be the predisposing factor.
are other possible causes
2.second possibility is,ALLERGY;leads to SINUSITIS
x-ray for PNS may confirm the diagnosis
I hope this is helpful for you, thank you