Ecg, heart ultrasound & blood normal, but 1 month after covid, my heart keeps racing with small activities, like walking around the corner. last time my heart went to 170 bpm (while resting it is 72 bpm). how to get back to normal with long covid?

I would start by havng a cardiopulmonary stress test to separate & evaluate cardiac and pulmonary performance during exercise. If possible measuring oxygen uptake, carbondioxide output&ventilation as well as monitoring heart rate& rhythm should shed light on your status. A proper physical therapy and exercise program can then be outlined for you depending upon the findings. Discuss with your MD.