This has been going on a for a few years now. I'll be doing normal things that I do, reading, driving, watching TV, walking, etc - and suddenly, my heart is beating very heavily and stumbling over beats. I can feel it through out my entire chest and sometimes it makes it hard to swallow or breathe. Then, like a flipping switch, I'm normal again. It leaves a pain, though, just below my collar bones behind my ribs, and it lasts for the hours afterwards. I'm never sure what to make of it, and anyone I've asked has either told me that I'm just stressing too much (which, at the time that this happens, is never the case) or that they have no idea what to make of it. Honestly, I'm not sure what to do about it. Advice?