Sorry to hear that you're experiencing those symptoms. It sounds as if that you're really monitoring the sensations that pop up in your body and there seems to be a lot of reassurance gathering and checking involved with your anxiety especially with the ECG. It can be really hard to let the health anxiety go and trust me, there's heaps of people out there who experience the same things too.
I personally have gone through a similar cycle with you with other health worries and constantly seeing my GP and checking my symptoms with myself. Fortunately though, I have gotten a handle on thoughts of that nature and changed my relationship with my body and mind for the better. You seem to have an awareness of the anxiety which is really good. Since you have this awareness, have you tried doing anything constructively with the thoughts and feelings?