I ran a cross country race today and soon after experienced dizziness, feeling faint, disorientation, and some nausea. I am a 15 year old female who is fit, eats very healthily, and is of a healthy weight. You may wish to note that I am currently taking roaccutane and have been for a couple of months. About 2 hours ago, I laughed and experienced a sudden sharp pain in the centre of my chest, in the upper sternum area. This pain is like a stabbing pain and is still there, particularly when I breathe deeply.