I'm Not Allowed To Feel This Way

I have not two parents, but four... that's a stepmum and a stepdad.
I have a widescreen TV in my room.
I have a PS3, laptop etc.
I have three adoring brothers.
I have pets.
I've always had a roof over my head.
I've always had food.

So I can't be unhappy.
So why am I?

I am regularly told I cannot be unhappy because even if they're aren't together I still have four parents.
Well, one is a manic-depressive alcoholic who cannot admit it, one is a man who would have left if it wasn't for my brothers, and I don't have the balls to move in with my father and stepmother not because I am concerned about my mother - although I care for my brothers like a lioness with her cubs - but because he will set strict rules. And I have a bit more freedom here. So selfish.

I have been bought and paid for all my life, yet it seems more like a 'we do this, so you must love us. You're so ungrateful'. I should be grateful. If I am in my room with my PlayStation 3, it means I am not downstairs hearing my name shrieked at me until it rings in my ears, a pair of sickly green eyes glaring me down until I'm five inches tall.

I almost ate an E when I was a toddler. I've grown up with my entire family smoking pot and taking pills, so when I express an interest in it, you allow me. But then switching around and telling me you disapprove? How dare you?!

You chose my A-Levels.
You chose my university subject.
You choose my clothing in your style, and get mad if I dislike it.
You make stupid rules, and expect me to live by them... I'm sixteen. Not six.

All four of you... I need my own space. I couldn't live with you.
I need somewhere to figure my own head out. And don't tell me I can't feel this way, because I have every right. You dictate everything else, but how I feel is under my control.