I recently got a canker sore for about a week and another appeared after that one healed and then another..why do they keep appearing?

Your description: Sounds like recurrent apthous stomatitis or a trauma ulcer. There is a relationship to immune system issues. These can be quite painful for a few days, then they hopefully resolve. Avoid acidic foods & toothpaste w sodium lauryl sulfate. Look for zilactin b at your pharmacy. If these lesions are not gone in 10-14 days let ur dentist evaluate the area. There are prescriptions to help as well.

Not normal: Certain diseases can be associated with sores in the mouth . To start, check with your dentist. Have you had your gum professionally cleaned in the past 6 months?