Can Palpitation Be Due To Thyroxin?

I have been put on thyroxin only 25mg per day and been on it 2 wks for underactive thyroid i had palpitations first few days, went back to doc he said they would go away , they did , but now i;ve just had them all the time for last 48hrs almost all the time . what can i do to stop them . should I stop the tablets?
Diana