My back keeps hurting! Please help don't know what to do?

my back be killing me most of the times. I already went to the emergency room for it and my chest but they did xrays on me and stuff and found nothing wrong with me so all they gave me was ibruprofen. Why do my back keep hurting it? It hurts all over and the sides of my body too and sometimes my breasts and chest area too. Sometimes it hurts to breathe in real deep. And it feels like its all tight and stuff. I'm a female and my age is 16? Am I a little too young for all of this to be happening to me?