My chest really hurts?

I've only had this a day but my chest hurts just above my sternum and it feels tight and i can't breathe as well as I normally can. It also feels a bit like something could be stuck but I haven't eaten anything which could have really got stuck down there. It hurts when I breathe in and out and It hurts right in the middle. I'm only sixteen so it is a bit weird. What should i do?