What Causes Severe Pain In Chest Radiating Towards Shoulder?

I am a 20 year old female. I smoke about a pack of cigarettes a day. Only known heart condition in the family is mitral valve prolapse. I have never been diagnosed.I was in a minor fender bender about 3weeks ago. The seat bealt was on. The impact of the air bags did break my thumb resulting in surgry 2weeks ago. There was no exam done on my chest.Okay, my concern.A few days ago, about 3, I had a day where I just felt kinda sick for no reason. Along with this was sharp stabbing pain in the upper left side of my chest. It starts under my coller bone and gets the worse at almost exactly 3in below my collerbone. It hurts to move, to breathe, to lay down. It s extremely tender to the touch, the 3in mark below my collerbone being the worse. I can lift my elbow and hold out my arm with no pain. This pain is very bad in my chest. It s hard to do a lot of things. It won t go away. It radiates into a dull pain in my shoulder.This pain got better the next few days and then came back even worse this evening.Do you know what this might be? I m starting to get really concerned because it s pretty severe pain. If I breathe in and apply pressure to the left of my chest it s a 9 on a scale of 10.