Why am I so tensed and worried about the psat/sat?

I am a sopre and I get straight A's in school. I am taking all of the honors/ap courses offered to sopres. But, when I took the psat freshmen year, I didnt so well. I thought it was because I didnt learn the material yet. When I took it again sopre year, I didnt do well too. What do I do? Granted, I didnt study much. But, I got a 158. Will colleges look at it? I want to get into ivy league schools. I am losing my confidence in me. :( Please help!