Hello and welcome to the forum. That is so incredibly frustrating when we can't get doctors to continue to work for a diagnosis when it isn't completely obvious initially. I'm just going to give some further ideas to look into. One simple one and obvious idea is that of dry mouth that is chronic. It can cause your symptoms. https://www.mayoclinic.org/diseases-conditions/dry-mouth/symptoms-causes/syc-20356048 One thing that can cause it that people often don't often realize it is nerve injury to your head or neck. There are prescription or over the counter mouth rinses to help with this. An image of your salivary glands wouldn't be a bad idea at some point either.
Since you have repeated candida over growth of the mouth, are there other indicators that your immune system is weakened? When you had your blood work done, did they check your sugar level to make sure you were not diabetic or pre diabetic? Sugar can build up in saliva when that is the case and cause symptoms.
When there is frequent yeast overgrowth, they typically recommend cutting down and eliminating as much sugar as you can from your diet. You sound to be clearly hydrated.
I would attempt one of the mouth rinses to see if that helps while you wait to see a doctor again.