What Causes Recurring Heart Palpitations?

My heart thuds so had it's driving me nuts. My cardiologist says everything is relatively fine. It doesn't register to anyone but me apparently. It is very hard to get to sleep with it being so bad and now it's as bad when I'm awake. I've noticed I can no longer eat chocolate without getting it going. Also, it will act up when I don't eat regularly so I have to eat every 2 hours but just a little bit. I was diagnosed with reactive hypoglycemia. I also had A-fib and eventually had a Cardioversion, something I never want to go through again. This does not seem to be related to any of my heart 'problems' but maybe more to my diet yet now I can't seem to get it to stop feeling like this at all. I feel like my heart will pound out of my chest any moment. I also feel it in my neck. I just don't know what to do next.