Painful chronic ulcers. Pl. help.

I have very painful Mouth ulcers mainly on tongue, pellet and inner lining of lips or cheeks. Pain is so much so that I cannot eat or speak sometimes. This prblm started 3 month back and ulcers are simply not getting cured/reason is  a not  diagnosed still. I have shown it to 2 MD general medicine, 2 ENTs, gastro surgeon and physicians. With medicines from each of these doctors, there was temporary relief but as soon as those medicines got over, ulcers used to come back again. I simply don't know whom to show and how to get it cured. What could be the reason. I am scared if there is something terribly wrong in my body. I never had ulcers before . I have PCOS and I am taking homeopathy medicines for it and ulcers as well. (I live in Hyderabad). Pl. help.