I Have Have Been Getting Jolts In My Heart

Hey! A lot of strange things have been happen to me lately. Time to time, I've have been getting jolts in my heart . I though it had to do with my diet but there's nothing wrong - I run Track/XC year round and pretty much each what's on the food pyramid. I then though it might be a stress problem, and it might be. Lately, I haven't been concentrating on my work in and out of the classroom - for a minute I might pay attention then the next daydream about something else. But to be honest, I have no clue what it is. I've asked other people and they say heart jolts happen time to time to them but I'm not really sure ...