What should I do!? PLEASE HELP!?

Hi my name is Ena. for the last 3 weeks I have been thinking that I'm fat so I decided to go on a little diet. I'm 13 years old and I'm 5'3 and 111.4 - 112.7 pounds or maybe I'm less, I forget. I used to be 122. My parents got really concerned over why I lost so much weight and they told me that I should start eating more unless I wanna end up in the Hospital. Well, I TRIED I gave it ALL to eat but i have no appetite for anything. I mean, here and there I do and sometimes I take a little choco bar but that ends up being the ONLY thing I eat the whole day. So this morning my dad made me eggs and I ate as much as I could. I really wasn't hungry but I didn't wanna get him worried so I started eating. When I was done, he came in the kitchen to see how much I ate and it turns out, I made him even more worried. He said that I didnt eat ANYTHING. That he threw away EVERYTHING. This was a LIE! I ate as much as I could and i must admit, I ate very good! I didn't leave a lot behind. He told my mom this and now they are planning to take me to the doctors to see if I'm ok. He said I'm stupid for trying to go on a diet, that I'm FAT and that I can NEVER be pretty like those other girls. I guess you can say that I am stupid for going on a diet but why did he say that really rude thing about me NEVER being pretty like other girls? Did he do this cause he was mad? Cause he was mad when he was talking to me so why did he say that? It really hurt me! and If i try talking to me about it, he'll say, you're crazy. WTF?