What Causes Daily Heart Palpitations For 3 Months And Overt Hypothyroidism While On Eltroxin?

Dear Doctor, I have heart palpitations since last 3 months and i have seen doctor with ECG ,2D Echo and Chest X-Ray and said that there is no issue in the heart, but still heart palpitations are recurring daily. I can see 2 doctors but 2 are saying no issue. Even i dont know why these heart palpitations to me. Can you please suggest what kind tests/medicine can cure for my heart palpitations. NOTE : Eltroxin used as my TSH is 14.5 & completed 2 months. Do we need to test again.