What is wrong with me?

I am thirteen years old, [female.] and i weigh 136 pounds. My doctor said i shouldnt be anymore then 130 pounds. I refuse to wear any tight clothes because i hate how i look. I cry all the time about my weight. I run and jump rope everyday but nothing seems to happen. I whisper horrible things to myself like "just kill yourself, everyone hates you Mandy. You are an obese *****" I scratch myself with my nails and leave scars behind because i do it so hard sometimes. Sometimes thinking about my weight i'll punch walls or break things. It's really horrible. I have considered suicide and sometimes i even make myself puke up my food. I'll go days without eating at all. What is wrong with me? I need help. Do i have a mental problem?