What would you do if your mouth, especially your tongue, and even sometimes your lips feel like they burn and sting all the time I've been to the doctor with this, only to get nystatin mouth rinse, you gargle and swallow - put the medicine in both cheeks.

There . There are other issues that can cause this. There is a thought that some vitamin and mineral deficiencies can cause mouth pain. There is actually a condition called "burning mouth syndrome" that can cause these symptoms. Be sure you are eating a healthy diet with and consider a vitamin supplement, but as this has been persistent it would be reasonable to have blood work and further medical evaluation.
Not Yeast . Its entirely possible that the condition is not a yeast infection , hence Nystatin wont work . Many oral conditions, vitamin deficiency, lichen planus, hormonal deficiency, medications, dry mouth, etc. May cause burning tongue and mouth. See a good oral surgeon or oral pathologist at a local dental school.