What Causes Excessive Sweating And Palpitations After Taking Synthroid?

I am a 34 year old femal. I am 5 9 and 178lbs. In 2001, I had to have my thyroid removed because I had a begnin tumor in it. I have been taking synthroid 250mc 1x s a day. Recently my doctor changed the dosage to 300mc, but for the past week, I have been sweating a lot and everywhere, it has became overwhelming!! Now my heart is palpatating a lot as well. Please advise as I am now scared. Thank You!!