Why do i get this tap, tap tapping in my ear constantly. started overnight, driving me nuts.?

Hearing loss?: It may be from hearing loss, did you go to a loud concert or something like that before it started? If so it may still go away in few days. If you have any pain in your jaw when you yawn, it may be inflammation in the jaw joint or tmj.

Ear or TMJ: Could be an ear problem anything from exposure to loud noise to infection. See an ENT specialist if problem persists. Could be the cartelagenous disc in your jaw (TMJ) joints popping in and out of position. If poroblem persists, see an orthodontic specialist.

Eustachian tube: If you can relate this to jaw movement this is likely just some swelling in your Eustachian tube on the affected side.That tube connects the middle ear to the back of the throat & allows mucus to drain out & air to come in. Jaw movement straightens the tube & can allow air movement in. This is common during URI's or allergy events. It should fade over time.