I am in my late 30s and have always been prone to worrying about my health (always imagining the worst !) but in general pretty healthy. Very slim and never smoked, etc.
Anyway, I have recently noticed that if I run for the bus, etc. my heart does that thing where it feels like it's almost going up to your throat, iykwim. Strange because I think I am reasonably fit. At other times have also felt like my heart is beating too fast or does a little skip.
Today I had an ECG and while it was being done (with my lying down) my heart started racing (the woman said it went from 80 to 120, whatever that means) and she thought it was odd and asked me if I was nervous. Anyway, I am quite worried. I then went shopping and felt fine...
I will be going to see my GP to follow up on results, but in the meantime can you reassure me that I am unlikely to drop dead? 
I am think I probably am quite anxious about lots of things and am a bit sleep deprived. (Generally have always had 8.5 hours sleep but over the last 2 or 3 months it's been 5 or 6 hours.)
thank you !!