Lets see if this is you.
Your tooth hurts, but only sometimes.
Its not sensitive to changes in temperature.
It hurts to bite on things but only every once in a while.
You have asked your dentist but they can't find anything wrong with it.
You may have a cracked tooth.
Cracks are not always visible by the dentist.
It takes some time and investigation to find them.
Once found however, depending on the severity of the crack, they can be fairly easy to fix.
So if you find yourself having random tooth pain that is driving you crazy, consult your dentist about whether or not your tooth could be cracked.