What causes small wounds in the mouth to suddenly appear? And how can you treat them?

I brush my teeth every morning and night and I don't eat/drink from stuff other people drank/ate from, I'm not using the same cup for more than 1 day and I'm not eating extremely crunchy things that could scrath my mouth but every now and then I get a really painful wound in my mouth that can last up to 2 weeks (usually it's only 1 week though) and no matter what kind of medicine I tried putting on it, nothing helped. I even tried putting alcohol on it but other than causing me immense pain, it did nothing to speed up the process so honestly I have no idea what to do at this point, it doesn't happen too often but when it does, it really gets in the way, even speaking is painful at this point. Does anybody know what's causing this or what I could do about it?
Answers

Tavy

Mouth ulcers very common in teen years. My son used to get them. Plenty of Meds at the pharmacist.

Anonymous

If it's in your mouth it maybe traces of some cleaning/descaling product. I once developed sores in my mouth years ago from using CLR in the kettle and I washed that kettle a half dozen times.Finally got rid of it and bought a new one. Never got them again

unknown1

Canker sores. Can't do anything about it.