I've had a sporadic chest pain, left side at the bottom of my pectoral that has usually happened about the frequency of once a month on average for the past decade. It is a stabbing feeling like something gets stuck, then breaks loose, as if an object is impeding the flow of blood until the pressure overcomes the blockage and frees back up. It is a very sharp pain that last only a few seconds usually and the pain is gone instantaneously. I have only become more concerned recently when the frequency has gone up to several times a week. I do have an irregular heartbeat and have had a am a young (26) active male who exercises 5-6 times per week including aerobic. After speaking with a co-worker who seemed to experience the same things, it makes me believe I have something like mitral valve prolapse.