@gbnana I started same symptomps of heart pounding when I started having unusual discharge from my left breast following with swollen part of the lobuls. It became increasingly alarming when the pounding increased by just walking from my place to the elevator (short distance) and followed with diffiulty speaking (as if i ran a marathon) it stopped suddenly... when i discontinued the genesis prescription of Nexium: I took like less than a week (and allerg-tec(allergy sneezing& runny nose) i assumed the combination of theses 2 meds caused it. The pounding stopped but I still feel that the symptoms are coming back then it stops.
I tried drinking lemon water (no sugar), not sure if this is the reason that it stopped.
Thank you for menioning about the breathing @gbnana