My poor attitude?

Lately, nothing seems right about my attitude to my family. It is true that I have been acting a little cynical and reclusive for the past few weeks, but it is only because I am severely under pressure with earning exceptionally good test grades and constantly studying. I need time alone and I do not get much, because my mother is always nagging at me and comparing my messy habbits to other neat people- which is so annoying and terrible- and it makes everything worse. My mother, today, left the house in a huff just because I wanted to use the computer and because I wanted to study later. I didn't feel like doing all of my chores at the moment, and it made her so mad she decided to go shopping just to leave the house. Everyone is always on my back, and I constantly feel annoyed. I don't mean to be this way to others, but it somehow ends up that way. I don't know what to do. Please help me. And don't say "counselor", because I can use that as a last resort. Thanks. . .