I'm so stressed and I hate my body 😒

βž΅β„’βΊΘ΅βΊβ™€ β€’ "One of the best things that ever happened to me is that I am a women. That's the way all females should feel."
Can anyone offer some advice here? I'm in middle school and I recently lost about 15 pounds, but I gained 10 back. I weigh 114 right now, and I want to lose 20 pounds before Christmas. All of my friends are so thin and pretty, and I feel so ugly compared to them all. Whenever I see a photo from myself from when I weighed 120+ pounds I just want to start crying because of how fat I looked then, and I can barely stand looking at myself in the mirror for long periods of time because I hate my body so much. I know I need to get back onto dieting, but a part of me has just given up on ever being beautiful and a lot of times I stress eat because of how much anxiety I get over school. (I'm in all of the highest advanced/high honor roll classes, and I got a perfect score for my PARCC tests {they are like pre-SATs} so the expectations of me are high, and I don't want to disappoint anyone.) Everything is just really stressful for me right now, and I honestly don't know how to handle it.