Hi, there are many reasons for getting mouth ulcers. Considering your age, it might be due to sharp cusps of the teeth, dryness of the mouth, underlying systemic conditions, due to medications. Etc
please avoid taking pain
killers it will worsen the condition.
Avoid changing the tooth pastes frequently,
avoid stuffed foods like kukure, lays,
chew gelusil tablets for 1 week (3 times daily. It will neutralise the acidic nature of the mouth.
Please visit a dentist
immediately to avoid things getting worsen.