question: I have had an ulcer in my mouth for almost 1 month now. It hurt at first, but it doesn t now. The problem is it stays there for almost 1 month without any sign of healing . Its size is about 3-4mm. I can see its bottom is red, it s bordered with a quite yellow round. I went to several doctors including: dentist , cancer, dermatology doctors...but none of them had any doubt about it. They said it should be gone but it will take long to heal. I m really worried. I m living in Vietnam.