There are multiple reasons for oral ulcers, especially recurrent ones. A proper clinical examination will be required to arrive at a rational diagnosis. A detailed clinical history will also be required for the same. The reasons can vary from stress to viral infections to gastric upset etc etc. Please visit a dentist for better evaluation of the case. The right treatment can be suggested only after the right diagnosis has been made. Alternatively, you can post the clinical photograph of the answers for an online discussion with the specialist on Practo. Your clinical history can be answered based on the questions raised by them. Regards.