I have had recurrent ulcer on the tip of of tongue for about 3 years now on the same spot that spread on tongue, what is it and what can i do about it?

See doctor: You have had this stop for a long time and now it seems to have spread. So time to see doctor for evaluation

Three years: is a long time for a mouth/tongue ulcer to keep recurring. Hopefully you have discussed it already with your dentist at a routine visit. It could be something as simple as a canker sore but even at your young age a mouth cancer must be excluded, especially if you smoke or drink excessive alcohol. Return to your dentist, an oral surgeon or ENT specialist doctor. Good wishes:)