Is it nirmal to have tachycardia during pregnancy, 20 wks pregnant with twins resting hearbeats 106 if walk goes as high as 186.ecg scans are fine?

Not unusual: It may not be "normal", but it is not unusual to have a high resting heart rate during pregnancy, as the resting metabolic rate has to increase (to pump enough blood for the fetus). Also, the blood volume increases, along with total body water, & these changes place a stress on the heart which responds by pumping faster. The normal ECG is reassuring. Rest! Best of luck w/ the pregnancy, & congrats