I am 13 years old and I weight 178 pounds I really try too keep weight off but it never sticks and I'm sick of being that fat girl when I was in middle school the "popular" people called me fatty it was horrible I want to lose at least40 to50 pounds what makes it worse my mom is always touching my stomach and saying I look pregnant and fat and it really hurt my feelings and confidence Help me!

I need to build musle and lose a lot of weight help

Hi, bro. Here are some tips:
First, you need to reduce your food volume and add times. Such as 5 meals a day, and at each meal you can only eat a little. Keep away from high-fat food. And add more protein food.
Second, running of more than half an hour can be a good way to burn fat. Fast walk is also a good manner.
Third, you can ask some of your friends or family members to monitor you.Or you can ask your friends to join you working out.
Forth, insistence is the most important thing. Without insistence everything you do temporarily is pointless.

You need to speak to your doctor about this. He can recommend a good diet program, and fitness routine for you to SAFELY stick to.

And please talk to your teacher or school adult about your mothers behavior. That needs to stop.

What grade are you in now? You say you are 13, but then say 'when I was in middle school'
Are you still in middle school? Or did you start high school a bit early?