Hello!Thank you for posting here.
You did not mention if these ulcers heal and come back or it is a single ulcer you are suffering from 3 months.I suggest you to see a oral pathologist for a biopsy
.Use a soothing ointment like quadragel on the area before food.
The best method is to do warm saline gargle thrice daily.
Have multi-vitamin supplements with b-complex.