I took Nystatin many years ago but never had any bad reactions, so I can't really help. But .. what did your doctor say?

When I took it, my doctor said there was really no way to know if I had Candida or not, but that if I improved, then that meant the Nystatin was doing something. So maybe you're having die-off symptoms from the yeast?

Either that, or there is some sort of bad reaction to the drug?

I would go over it again with the doctor. Good luck.