I have the same thing. I've thought that my heart beat has been irregular for a year or so now, just by counting my pulse and noticing that sometines it skips a beat & then beats twice really fast afterwards. Recently I've started going to the gym more often where the machines count your heart beat. Normally it lingers around 120-140, but then suddenly it will jump to 180-190 or more for a few seconds & yesterday actually reached 216 - which is 15 more than my maximum heart rate. Im 19 years old, 5'7' and weigh around 142 lbs, and I'm quite worried about this, but people just laugh it off and say that the machines must be inaccurate. I think that maybe a doctor will say the same.