Pain in my chest is freaking me out..?

I am 14 yrs old and i dont think im overwieght but i am freaking out because i dont want it to be a heart attack. i tried to lay down and stretch but it hurts and its like a warm felling every so often.. My dad has a chestt plate thing (haha sorry) that is inwards and i do to apparently. Could this be the problem? I dont know what to do.. Any ideas what this could be?