I have been the same way, in just the last year only, though I've had generalized anxiety for about ten years. However, recently, among all the other little conditions here and there, I had a little opaque, whitish patch develop on my bottom gums behind my last molar - where my wisdom tooth was removed many years ago. (I only noticed this while looking in there with a pocket flashlight for other reasons). My first thought was that it was from chewing preferentially on that side, which I had been, and that it was merely a benign keratosis (callus).
Then, just like you said, HA is asking me "is it really that though? Or is it [dun dun dunnnnn] something else?". So, after doing the inevitable - Googling - I looked up "white patch in mouth". MISTAKE. You can only imagine where that led. It immediately became a slippery slope with all the usual doubts and worries. After getting over all the usual HA worries last year, Parkinson's, MS, ALS, lymphoma and brain tumors; I felt pretty good for a while. Then that stupid thing in the mouth popped up.
I'm finally out of the woods on that one, and not worrying anymore about the other things like aches, pains, feelings, and sensations. My recent relapse has tended to be more towards things that I can see with my eyes and feel with my hands, e.g. lumps, bumps, scratches, patches, blemishes, and sores anywhere including the mouth. Although, right now I have an itchy index finger with no rash, no bugbite, no known reason - and like you, am trying to avoid being derailed into thinking it's something sinister.