Some yeasts are resistant to the azole drugs, like fluconazole (Diflucan
). So that is a possibility. However, yeast infection
doesn't usually cause discrete ulcers. If so, taking additional Diflucan won't help.
I'm confused by your description of the sores. "Not open", yet looks like canker sores, which are open ulcers in the mouth. Red bumps could be yeast, or any number of other conditions. An allergic reaction to monistate or some other irritant also might be possible.