What just happened to me?

I just had this EXTREME sharp pain in the right side of my chest & it got more intense until it felt straight like my chest was literally on fire. I thought I was having a heart attack but I'm only 21. & it happened while I was laying down, so I sat up. I thought it may have been due to pressure from my breast because I'm a D cup but the pain was way too intense. It only lasted about 30 secs and was in a small section in the upper right part of my chest. Now I'm laying down again & I can still feel a little stinging in the area but definitely not unbearable. What could this have been?