Go find a mirror. Look at yourself. Point out what you hate about yourself. Write them down on paper. Look at what you wrote. Crumple up the paper. Throw out the paper. Go back to the mirror. Find the things you like about yourself. Write them down on paper. Circle those things on the paper. Underline them. Remember them. Tape the paper on your wall, or your mirror. Put the paper somewhere so you will see it everyday. Tell yourself you are beautiful already. Do not go out and buy tons of makeup. Do not buy expensive clothes. Wear what you like, and be who you are. You are in 7th grade. Enjoy it. Don't ruin it by trying to be someone your not. I went through 7 and 8th grade wearing the most boring clothes and no makeup, but I was still called beautiful, and I had so many friends who didn't care one bit what I looked like. Everyone is beautiful in their own way. Hope this helped (:
You believe you are. You don't need to be beautiful (although you are) to fit into 7th grade. 7th grade is mostly just full of preteens who are trying too hard to fit in. Stick with your friends (or make some!) and you'll feel much better being with real friends than people who just want to be with you because you're pretty and preppy.
I'm sure you are already beautiful, you just don't realize it. Beauty is on the inside anyways. And if you're thinking about wearing makeup, don't. At least not in 7th grade, maybe you can try a little when you reach junior year in high school. :)