Yupp. This is common in Fibromyalgia! It is often DX as TMJ disorder of the jaw joint. I am not DX with TMD (can't afford a dentist), but I have only recently experienced difficulty with eating because I have trouble
opening my mouth at times-- it just clenches shut! I think it's important to make sure by a dentist that nothing severe is going on with your teeth, but if they say nothing wrong, it very well could be from the Fibro, and arthritis too since you say you have that! I get terrible pain in my jaw, face and head. Just terrible, horrible, wretched pain! Bruxism (grinding of teeth) can also be found in some Fibro people because we tend to be more anxious than the general population! I, too, used to grind my teeth at night as well as clench down a lot... I'm not sure if I still do, but god, do I wake up in a lot of pain! A mouth guard should be something I look into too. I'm sorry yours didn't fit. It sucks to not be able to afford a special-made one... I would be in the same boat! Can't afford anything that I need to feel/ get better! Ughh
But yes, to answer your main Q, it is very common in Fibro. All of these issues are. I [literally] feel your pain!
Love,
Eden