I'm seventeen, I don't smoke and I hardly ever drink liquor (twice this year) so my heart shouldn't by at a large risk, but sometimes I feel like it shakes, sometimes it beats extremely fast and sometimes it beats very heavily. The other day I suddenly felt dizzy and nauseous so I had a glass of water and took my pulse, the first minute it was 96 beats per minute, a minute later it was 80 beats per minute, and minute after that it was a 100 beats per minute. I have no idea what's going on in there and I know very little about heart diseases. I admit I'm not very healthy, I am overweight, but I have never had any heart problems and always had a little bit low blood pressure. There are no heart conditions in my family but I think my grandma had diabetes and so far I haven't looked that much out for sugar. I do drink too much soda and caffeinated drinks but I am more careful about my diet now than I have ever been. I have been a little bit stressed these last few months, but probably not enough to do something to my heart. I hope someone can give me some advice on what it might be.