For the last few days my molar tooth on the top hurts of i stomp or jump ( only at the moment of impact). no other pain. what could be up?

A couple of things: Here are some possibilities. It could be an infection. It could be sinuses. It could be widening of the periodontal ligament. It could be periodontal disease. A clinical exam with x-rays & periodontal charting would be necessary. It is impossible to give you a diagnosis due to the limits of this forum. I suggest you see a dentist to help you find the exact answer to this problem. Wishing you well.

Possibly: Possibly a problem like a cavity, or a crack in the tooth. If this problem has occurred for more than 5 days, get it evaluated by a dentist!

Sinus infection?: Sinus infections an cause upper back teeth to hurt even though there is nothing wrong with the tooth. You also could be grinding your teeth and putting extra pressure on this tooth in the process. You really need to have a "hands on" evaluation by your dentist so they can help you figure out what is going on.

A number of things: If your teeth don't touch when this happens, it is most likely an inflamed or infected nerve or a sinusitis or sinus infection. If your teeth do touch when this happens, then add a bite discrepancy or fracture in the tooth or root. Your dentist should be able to easily figure out the cause of your problem.