As most other people pointed out, you really need to visit your doctor and have him check to make sure things are okay, but I just wanted to say that I had something similar off and on when I was younger. I specifically remember the pain I felt when I breathed normally -- I had to take shallow breathes for a minute until the pain went away. My doctor told me that it was quite common amongst teens who were growing/developing. So no need to get worried, but definitely ask your doctor just to be sure it isn't something serious.