Everyone on the planet does. The beats are actually a back-up system for the heart's normal electrical system. ALL of the cells in the heart have the ability to fire impulses off; this is perfectly normal. The problem you are having is actually your anxiety which will make this happen more often; it's because you have increased your body's adrenaline level which in turn increases the premature beats......it's called a 'fight or flight' issue. calm yourself down, try to stop worrying about it and it will probably not bother you too much after that.
everyone has ectopic beats, these are like a back up system incase the sa node fails.
the worst thing you can do is worry about them this increases them, i would kinow from past experience :)
if your heart is doing over 100 bpm then get ur bloods done if u havent to check the thyroid, this can cause a panic attack feeling but will need treating
good luck n remember ignore them and u wont notice them :)