Echo, EKG and Stress Test OK but heart won't calm down, breathing fast, air hunger & neck pulsates a lot esp upon standing up. What could it be?

You may have a. form of autonomic dysfunction (dysautonomia) called POTS (positional orthostatic tachycardia syndrome.) Your health care professional should be able to diagnose and threat this for you. If not locally try a University center for evaluation.