Heart rate around 150-160 while standing and feeling really dizzy. been having chest pain but all my heart test come back normal, what could this be?

Many Things: Unless there is an arrhythmia, a high hear rate is usually not caused by the heart itself. It is like a ship in the ocean, buffeted by hormones and drugs in the body. I assume you were checked for anemia and thyroid problems. Check your intake of caffeine, decongestants, diet pills, and natural herbs like guarana.

Several items: Paroxysmal atrial fibrillation or flutter, WPW and more. See cardiology and get Holter monitor to discriminate the rhythm.