These are very common symptoms, usually attributed to preventricular contractions (PVCs) or preatrial contractions (PACs). The electrical impulses get a little haywire in there sometimes and cause a feeling of a skipped beat, when in actuality you have a beat followed by a premature beat and then a longer lag time than normal (the "skipped" feeling). Many, many people experience these, and most undergo a cardiac work-up (EKG, stress test, or echocardiogram) to rule out any major problems. Mine started when I was 14 years old. They can be brought on by too much caffeine or alcohol, certain medications, and stress or anxiety. Some people take medications called beta blockers to prevent them, but usually they can be controlled (or at least become tolerable) without medicines. I've found the best "cure" for a long run of PVCs, for me, is to take a brisk jog for about 10-20 minutes. Sort of "shock" your heart back into a normal rhythm!
I still get these episodes fairly frequently, surely at least once a day, and sometimes (if I'm sick, had too much caffeine, etc.) I'll get a long run of them that lasts hours, sometimes even days, and then I know it's time to change something I'm doing! Cut back on the caffeine, take a run, do some meditation - these typically work best for me.
The good news is that 99% of the time, these "skipped beats" are nothing to worry about and are simply a nuisance. Sometimes a big, scary nuisance, but you have to be able to talk yourself through them. Depending on your age, family history, etc. you may want to get a cardiac work-up for your peace of mind!