Suggest Treatment For Severe Heart Palpitations

Hi Doctor, I spent yesterday in the ER with thumping heart beats i.e. palpitations. I had all blood work, a full panel, enzymes etc., EKG, chest ex-ray, and TSH (.04) because I ve had a total thyroidectomy. In October of last year I had a walking stress test and all the same tests then, all of which are normal, showing no sign of any cardiac issues. My palpitations are benign , I m told. Fine, how can I slow them or stop them with out some antirythmic meds? Of course even though I ve been told I m fine, I feel them and sometimes worry which triggers the stress bug, then my chest gets tight, I have to take deep breaths and eventually a half of an Ativan to get out from under the stress. Is there anything I can do relieve them? They really started when I started taking levothyroxine. Thank you, Amy