Hello, I am a 22 year old female and have been having a weird pain in my left shouler. It only hurts when I move it. It also feels like my whole arm is throbbing, like I can feel my heart beat through my whole arm. My chest doesn't hurt but feels weird, occasionally getting sharp pains. I noticed a really fast heart beat today that went away as fast as it came. Am I just over reacting, or So you think something serious is going on?