I went through similar situation. ER a few times, ekg fine. Follow up with dr, my tsh , t3 and t4 low, low vitamin d too. I switched to armour, that didn’t work. Then I tried compounding with t3 added. Was doing ok, but still had symptoms. Now I’m on tirosint, which doesn’t have fillers or dyes
I suggest having your vitamin d checked, iron too. And have all your sex hormones checked. As we age, our hormones decrease which can impact thyroid levels.
Also, with Lyme disease on the rise, would be good to be checked as well.