Chest pain-sharp, stabbing pain in the middle of chest?

[carolinagirl]

I am 25, and one day last week I noticed pain in my chest, and it gradually got worse as the week went on, and I started to have rapid/short breaths, the other day I went to the urgent care and had chest x-rays done, came back fine, had an ekg which was fine. It is a constant pain, nothing makes it feel better. The doc said everything looked fine, so he diagnosed me with a chest muscle strain and put me on some motrin, its been a few days, that hasn't touched the pain, and chest seems to hurt worse. It almost feels as if it is bruised inside when I press on it, a very weird feeling. He ruled out a blood clot-I'm on birth control so he was worried, but said its fine, no collapsed lung, no pneumonia, pleurisy, etc. Anybody have any clue what it could be? I really don't think its a strain, especially since the meds isn't working, I tried the heating pad also, no luck with that.