Talk to your doctor. If thrush is persistent, you can contact your doctor about a prescription for Nystatin (an oral antifungal liquid). If you have already used Nystatin and it did not work, Diflucan (fluconazole) is a stronger medication. If you are nursing, both you and your baby may need to be treated or the infection may pass back and forth. Also sterilize bottles, nipples, and pacifiers to avoid recurrence.
See your doc. If you've used the standard anti-fungal medicine, and used it just as prescribed, there are some other treatments that can be considered. (if you're breastfeeding, have you treated your nipples, too?) you should see your pediatrician, because there are some other things that might need to be looked into.