A lower dose may help -- the pain meds suppress TSH a little, but not usually dramatically, so would not assume the TSH is inaccurate. I'm not clear if you're on levoxyl or armour -- you mentioned both. Too much of either (esp armour) can cause this problem. Would not stop meds altogether but consider lowering the dose more drastically if every decrease has been followed by another decrease. Also ask your doc about other possible causes and consider whether or not menopause status may be contributing.
I too have been having this symptom, of a pounding heart, with throbbing in body and head, esp. at night and can notice it when I get still in the day also. I way diagnosed recently with Autoimmune thyroid disease and was in the state of hyperthryoid. This created a lot of palpitations esp. at night with irregular heart beats and pounding of heart (which is very noticable in my head also). I took beta blocker for a few weeks which helped a lot, then another tsh test showed a swing over to hypothyroid, although I never felt the symptoms of that, but kept feeling I was hyperthyroid, now I have weaned off the beta blocker and the pounding has returned every day and night. So my question is to the doctor and yourself is are you saying that hyperthryoid is causing the pounding and resulting throbbing in my body and head. My BP and it is fine. But I do have MVP (Mitral Valve Prolapse). What do you think? Also I am 54, and this is all new for me. I would appreciate anyones imput.