Hi Jim,
Not sure if it would be helpful or not for the thrush. I had the same problem with Nystatin burning. My 8 month old son had thrush a couple months ago, and the doctor started him with Nystatin with no success, then tried a different medication which they said was much better. The name of it is Fluconazole, and it cleared his thrush up after a little over a week, and it didn't come back. Not sure if it would be worth mentioning to your doctor, but thought I'd offer it as a suggestion.
Paul