OP
It's very ,very definitely anxiety.
you need to stop being upset/ashamed that you suffer with this, its like any mental health condition and as real medically as anything else.
I suffer with it too.. I had the same problem with the palpitations last Christmas, bad enough that I took myself to A&E after it going on all day, and they were lucky enough to catch it on the monitor while they were doing a trace on me.
By the time I got to the cardio team and a 24hr monitor it had all but stopped, they put it down to anxiety.
I didnt want to believe them as I've had anxiety for over 18 years, I KNOW my symptoms, but at the time I was under SO much stress with a marriage breakdown, my body decided to throw in the palpitations, chest pains and breathlessness for good measure.
Please try the sertraline, I used to take it and it DOES help, immensely.