I'm a 24 year old female. For the past few days I have been experiencing a pain in the left side of my chest, behind my breast. It's a pain that comes suddenly and then goes again almost immediately. however, although its sudden its more uncomfortable than sharp and once it starts it will happen on and off for hours. I've also had some discomfort in my left arm, although this has not happened much. I'm very worried about this and have no idea what it could be, any ideas?