Well try doing something active. when ever i feel really down i tend go running or dance. Music and meditating can also help but i know that doing summin energetic releases endorphins and that cheers you up. Try starting summin like running or gym or dance etc, if u join a club u may even make new mates, sometimes it can just be boredom, i mean rite now i got 1 year left before uni, ive got good grades, no pressure frm skool, but im bored so my mood has been fluctuating. maybe your bored with your life and want to have a change of scene if you get wot i mean?