I have been to the ER three times within 6 months with panic attacks which I was sure were heart attacks. It is a terrible feeling, and be sure that you are not alone.
How I have decided to handle it from now on is to be fatalistic. When they come up, I just say to myself. OK, If I'm going to die, then so be it. So far so good. Of course I am an old man, and you probably are young, so maybe it would not work for you. I do wish you well in your struggles with this debilitating, scary health issue.