I Have Been Experiencing Heart Palpitations

I have been experiencing heart palpitations. This is not a new occurance, it just seems more aggravated lately. One year ago I had mono and got pericarditis. I had an x-ray, echo, holter monitor for 24 days. My cardiologist said everything seemed fine and that I was healthy. Recently, I was sick with a virus and my doctor thought I had it again. My symptoms were: discomfort on my left side/rib area, that spread around to my left mid back. There were two days where I also experienced sharp chest pain in one spot. Then the next day I had the same sharp pain but in my back at the level where the chest pain was. That went away finally, so did the discomfort in my side. Now that I'm feeling better, I have been having some very scary heart palpitations. It causes me to try to catch my breath and I also lose my appetite. What do you think is the cause of this and do you think it was pericarditis that I had again. Or do you think the issues I'm having are different?