Please help, I'm insane!

How do you figure out if you have a mental disorder without alerting your parents to the fact?
I think I have insomnia - ie an average of 4 hrs sleep a night - I'm going all antisocial, I'm pretty much paranoid but I don't care what happens to me, I have an alter ego that comes out when I'm angry, and that is very dangerous at times.

I know I need help, but I dont want my mum to know coz I dont want to be treated like I'm insane.

But my mood swings are giving me friggin whip lash coz I go from sad to happy to angry to energetic all the time and it's affecting my work and social life (school isnt in at the mo, so it's not affecting my schoolwork).

Another thing, I have an obsession with the Joker that is distracting me from... well, from life. I get all depressed whenever I start thinking about Heath Ledger, coz he was my idol and he died... And I didnt even know him!!

I'm also having problems feeling any emotions... I don't care what happens to myself or any worldly possessions I have, but I also have nightmares whenever I get sleep in which my friends and family die...

Please help, anyone know what I can do??