This this thought bothered me for years now... i have a cavity... why does it only hurt when i eat something really sweet or really cold?

Stimulus: The bacteria festering in the cavity produce acid when sugar enters the defect, which irritates the nerve. The cold stimulus irritates the nerve since it is not protected by enough dentin or enamel. I hope you don't have this cavity for years. A simple filling may no longer be an option. Don't wait until the pain becomes unbearable to fix the tooth.