hi i am a female and only 21 years old, and in good shape. i have been having chest pains on the left side of my sternum for about three days, it hurts really bad when i laugh, cough, try to get up from laying down, or try to switch sides when i am sleeping. i do not want to go to a doctor because i thought this would go away on it is own. but now it is really starting to irritate me. what should i do?