What causes low self-esteem in teens?

Do you think I am depressed? I am 16 years old. I absolutly hate school some days even though there is no reason for me to. I used to love going out with friends now I feel like I have to forse myself to go out with them because all i want to do is sleep or exersise. I am paranoid with food, I will only eat 100% healthy sugar free egg free food. only low caloire. I have to exersise for atleast 1 hour a day. I feel so guilty when I sit down because I feel like I am getting fat. I have panick attacks on most days is things are not organised. I don't want to live somedays I wish I could die. It seems like absolutly nothing goes right in my life. like everything is 100x harder for me. I feel unbelieveably fat eventhough I am medically thin. I have NO confidence or self esteem at all. I sleep so much and I dont want to see or talk to anybody latley. What is this?