Growing girl (12 years) and need help! Not getting all nutrients i need! Eating/health advice!!!?

Well, I'm 12 years old. I try to eat everything I need. I try to eat all my fruit, veggies, protein, dairy, etc. But, I eat about 800 calories everyday. I know that's not good. Though I try to eat everything I have to, i get full from small meals and i feel to full to eat everything i need. for example, today i was eating some rice and carrots and got full by that. i was checking my progress on my eating and still needed more protein filled food! so i made 1 1/2 servings of boca chicken nuggets to fulfill that. but it was hard because i was already full! and even if i try to spread my meals out, it doesn't work very well. i can't eat so much. help!?