Everyone has great ideas here, and starting good habits (cleaning, eating, excersizing) now will pay off later. I moved out when I was 19 because of a bad relationship with my mom, and I was in 1st year university. I had good habits when I lived at home, but I also felt I was too busy to do any of it and my apartment suffered when I moved out. But, we ate well and I walked/biked everywhere so keeping up good health habits was easy. Can you walk/bike to school? It's a good way to stay in shape. I just biked to work and it took me less time that taking the train and I feel fantastic!!
I also want to offer my kudos to trying to stay on track. It's hard when everyone is trying to sabotage your efforts.