Sorry to hear you are having issues, the extreme thirst maybe a something else. You may want to have your doctor check that out, make sure when you see your health care provider you tell them about your thirst issues.
Same thought as the poster above! You really need to get your glucose level tested soon, as far as I know extreme thirst isn't a symptom of fibro, not one I have heard of at least.
It could be medication that your on. Lyrica gives me a dry mouth but it is not a severe problem to me. I agree it could be a diabetes symptom, the only way to know for sure is to have your sugar checked.
I know that for two of my meds dry mouth and eyes are a side effect. But definitely have the blood sugar tested. Because you don't want to have undiagnost diabetes!