What are the chances that i will be put in the hospital for anorexia? ?

Im 13 and 89 pounds and 5′1, i have been suffering from anorexia for about two months. I think i am going to tell my mom soon, i only eat about 400 calories a day. I know if i tell my mom she will take me to the doctor, what are the chances that i will be put in the hospital? if im not put in the hospital what will happen to me?