You're not going mad. I've had this. A normal ECG is very reassuring, they can tell almost everything from an ECG, apparently there's 2 main patterns that they look for that need immediate attention. Everything else is inconvenient, often upsetting but harmless. Do whatever tests the doctor's want to do, but otherwise try and breathe if it happens, slow deep breath. Talk to yourself at that point too, telling yourself this is a 'surge' (or that's what it was like for me) and it will pass.
The other thing that helped me was not skipping or delaying meals (empty stomach triggered them), good sleep if you can get it, and plenty of fluids, it does make a difference apparently.