im a 15 year old girl. somtines i have a really tight feeling in my chest and stomach area, this tightness then becomes shooting pains. they sometimes heurt so bad i cant move. the only way to stop this is to lie on my side. i dont smoke and no faminly history of heart or chest problems. also my left ribcage sticks out more then the right and somethines when lying sdown and breathing i can hear/feel a starge poppong sound coming from my heart area. what could this be?