Tachycardia. Ecg often shows just sinus!

I m a bp and tachycardia patient since 2012 recently I was diagnosed with severe insulin resistance since treatment started I lost weight but my tachycardia problem isn't solved ,even after taking medicines many times my heart beat is 120-140 ,now I'm 23 and it's been almost 6 years and this issue has affected my studies as well as career , I'm  taking metropol 50mg in mrng ,metformin 500 mrng and night, lipoglyn 4mg mrng ,amlodopline 5mg morning and night ,losarton 50 mg mrng and night and prazolin 2.5mg in night . Few doctor suggested electrophysiological study of heart while few doctors said it's not needed that's what the biggest confusion is . MY 2D ECHO REPORT IS NORMAL BUT ECG OFTEN SHOWS JUST SINUS