Welcome to OCF. I hope your symptoms turn out to be nothing serious!

Not all ENTs specialize in the same things. Was the ENT experienced with oral cancer or were they more of a specialist for putting tubes in childrens ears? I would suggest seeking out another ENT, one who is more of an oral cancer specialist.

Dentists unfortunately arent always up to date with all the sores a person can have inside their mouth. Many dentists pay more attention only to the teeth and ignore anything else in a persons mouth.

Any sore someone has in their mouth for over 2 weeks should be checked by a professional. Its not possible to diagnose over the internet. Photos cant be checked with a biopsy. Thats what I would suggest, a biopsy which is no big deal. You may be sore for a couple days but by the time the results come back you will be ok. Waiting for a week to get the results can seem like its taking forever.

The white coating and yeast diagnosis sound to me like thrush. Has any of the professionals put you on anything for thrush? If so you may need another round. Plus if it would be thrush, you would want to change everything you have in contact with your mouth. That includes a new toothbrush, cup or glass you drink out of in the bathroom, etc. Even get rid of the mouthwash container if you put the bottle on your mouth. When I had thrush I would be fanatical about changing everything even my sheets.

Best wishes!!!!