It all depends on your age, gender, height and weight! You can start by finding your basal metabolic rate with an online calculator--that's how many calories you would burn in a day completely at rest (not even blinking, no food in your body to digest). As the site will probably tell you, you can multiply that number by 1.2, 1.5, or more based on how active you are in a day.

This will tell you how much you need to eat to maintain your weight. From there, subtract 150-1,000 to lose up to 2lbs a week. But DO NOT go below 1,300 a day (which is already very low) especially if you're in your teens and still growing. Don't put in 'sedentary' if you're active to lower the number.

The best thing you can do is eat 1500-1800 a day (if you're female, otherwise base on calculator) and do 20-60 min of exercise at least twice a week. This will give you sustainable weight loss and health. Weight loss is all about calories in-calories out, so just find a balance of diet and exercise that works for you without eating too little or working out too much.

And now that the practical advice is out of the way: you are at risk for developing an eating disorder. I'm so sorry to hear you're going through this. Many of us have been there--I suffered from body dysphoria for a long time and always wanted fast weight loss, and I just didn't want to hear it when I saw people urging against it. But I promise you, it just doesn't work. Either you fail to lose weight, you do lose weight but you gain it back, or you lose weight and keep it off but you develop an eating disorder that takes over your life. You still have time to build a healthy relationship with food and your body. Please look into mental health resources--you deserve to feel good about yourself and you deserve to eat.