stressed depressed & tired

I'm only 16 and I am usually a happy bubbly go to kind of girl but lately I've been so upset over any little thing and I don't know why. I feel like nothing I do matters, I do everything I am supposed to do and more I try and be the best daughter and the best girlfriend the best sister etc I can be but I feel as if no one notices it. lately I've been having crazy thoughts and crying spells and mad spells and I don't know what's wrong with me and I don't know what to do about it. does ANYONE know of ANYTHING that I could do to stop these feelings and crying spells?