Unknown intolerance and feeling a lot of fear 😰

Hi all, I’m new here. I just had some of the scariest weeks of my life. I was diagnosed with hypothyroidism a few weeks ago, technically still subclinical. Was having a few symptoms (mostly fatigue and weight gain) so was put on Synthroid 75mcg. About a week and a half later, I had racing heart and shortness of breath, which was terrifying, as well as aches and some dizziness. Dose was lowered to 50mcg and then 25mcg. Side effects continued. I ended up in the ER after going to urgent care 3x the week before — spent a night in hell, test after test, and they found nothing wrong with me. Said dose was probably too high and that it was my “anxiety” which I didn’t appreciate — who wouldn’t be anxious in that situation? Was told to stay on 25mcg, but continued to have same side effects. Finally went off the drug entirely, and can breathe again. Thank GOD! I changed doctors and also saw an endo. The endo said I may have had a bad reaction to some of the inactive ingredients in Synthroid and said in the future if I want to treat, to try Tirosint. She also said I don’t even have to treat if I don’t want to — since it’s still subclinical. Only case in which I’d need to be treated without question is pregnancy. I think the scariest thing right now is not knowing if I’m intolerant to Levothyroxine itself or rather inactive ingredients. I have also had similar bad reactions (racing heart, feelings of being about to pass out/panic) on other drugs like SSRIs, benzos, Moderna vaccine, and prednisone. Really wondering if I’m just intolerant to pharmaceuticals in general. Throughout this ordeal, no one seemed able to give me a definitive answer. That’s what is so scary to me. Any supportive thoughts would be appreciated.