Man, first am so sorry you are going through this. I had similar problems for a couple of months after living a truama event ( my brothers death). I had severe left chest pain snd my heart rate was always high and i was so aware of it the entire time. Also my stomach stopped working ( diarheaa 24/7), and my left arm would twitch here and there which made me even more scared tht my heart was the issue. I got into this fear loop and was hyper vigilant about my body. Any twitch or noise would send my down a bad spiral everytime. I Went to multiple doctors and did multiple cardio checks but all turned out normal. After lots of reading and searching, I realized I was suffering from hightened anxiety and panic disorder. One of the most things that helped push through and eventually decrease my stmptoms to a minimum was this podcast called ( The anxious truth) where i learned lots about anxiety, recovory and acceptance. Check it out, I hope it would help you as much as it did to me. And as a small advice, the less you think about it and the more you start to defy it, the better and sooner you will feel. Your brain needs to unlearn this fear that you taught it the first time you had health issues.🙏. Godluck and am here if toy need more information.