I'll answer your questions individually. 1.My doctor does not feel I need to undergo Holter test, Do my palp. Most likely, you have PVC's which are benign given your age and your normal echocardiogram. However, you do experience symptoms from the PVC's so you should avoid tobacco, alcohol, caffeine, and stress which can all precipitate PVC's. Medications called beta blockers can suppress PVC's but they have many side effects like fatigue and impotence that would preclude using such a medication in someone like yourself.
Many young people have nonspecific t-wave changes on their ecg's with normal hearts.
I agree that you do not need a stress test. Thus, heed your doctors' advice and exercise as you would like to. Echocardiograms only determine the structure and function of the heart, not the rhythm. ECG's can pick up a tachycardia and help to diagnose the cause of it if the tachycardia is occurring while the ECG is being performed. I hope you find this information useful.