It seems on the left side it is most common just under
my left breast, where i feel my heart beat the strongest. The pain
comes suddenly, last a few seconds up to a few minutes and then goes away. Sometimes, but rarely, moving in certain ways might produce pain but im not sure if that's just coincidence. I was having heart palpitations and now for the past few days, my heartbeat has just slowed. I've increased my physical activity, but I'm not over loading myself.