I don't know if I have a cavity. I think I might, and it hurts sometimes. I went to the dentist 3 months ago, and it still hurt then, but I didn't have any cavities. I've had about 5 cavities in my lifetime.
It could be something other than a cavity, gum problem, etc. Sometimes those things are hereditary. I'd check with a dentist & perhaps see a gum specialist. Hope it feels better soon!