Sharp middle chest pain last a few seconds for weeks now, previously had ecg, EKG, heart monitor and chest xray all came up ok, what could this be?

Sharp chest pain. It could be pleuritis or pericarditis. Get your ESR and c- reactive protein to be checked. If it is elevated then you need anti-inflammatory medication like indomethacin. Other differential is costochondritis, which also responds to an-inflammatory medication. Consult your physician.