There's no one simple answer to this of course. Why did you start taking these pills? How do you get them now? What do your parents say when you sleep all day ? Don't you have friend's to go play with? To me, sounds like you want to hear that you're depressed but if you were severely depressed, then you wouldn't be asking why? Make sense? Find something else to do, it's a matter of figuring out for yourself what's motivating slow self-destruction and avoiding living life.
What depression does, is not allow you to SEE and FEEL what happy people feel. They're not acting happy, they're just happy. This is what you need to find out about yourself, what makes "me" happy, and go do it. Keep things really simple for yourself and take one day at a time, like say I'm gonna start tomorrow and this is my action plan to start being happy and go DO IT. You have to start or you'll never get where you are going. Not taking action is an action in itself so if you keep taking downers, it's because you enjoy being down.