How do I start living my own life? I find it very hard to do thing for myself?

For the past 2 or 3 years Ive been living my parents lives. When I was 17 my dad became very ill with liver cancer, I took him to every single appointment, anything he needed I DID IT!!, I dropped out of high school to take care of gim. then sept 9th 2008 he got a liver transplant. I thought everything was fine. But he is deeply depressed and its on methadone. and takes too much. My mom just got out of the hospital with pancreantitis and celulitis. She is still stick but recovering. My parents argue every single day of my life. I just got laid off from costco my job. bec of the economy. I want to get my ged. go to college, lose weight, get a job, move out. But I dont know how too. I say im going to do all these things but they never happen. Bec im constantly consumed with depressed bec of my parents. I feel stuck. I have great intentions. But then when i wake up and there arguing and are all scrued up. It makes me very depressed so I sit in my room all day. I need some advice on what to do. I might just go crazy here pretty quick.