Need Help About Eating, Read More..?

Ok, im 13, and my sister has eating problems and has Anxiety, and depression. and my mum and dad are split up. around dece,ber time we had to move. Im not fat. but i have a little bit of a belly and chubby cheeks. i think not very highly of myself. at some point i think im pretty <- in a none vain way. and sometimes i think im ugly, and its usually ugly, and i always hate my body. and i used to snack loads after school, so i thought right thats the reason im gettin how i am blahh blahh blah, so i make a diet plan, where i have certain amount of preotein and carbs and fat in my diet and i should loose 1 pound a week. but its to hard for me. i used to eat just dinner and maybe breakfast and maybe a snack at break. but i ate 3 meals a day and if i was hungry have somthing wich isnt sweets ect. but its just to hard and ive hardly lost any weight. n i hate it. i hate myself. my appearance, im horrible to everyone, even my mum says i am. i find it very easy not to eat. at all. but i cant do that, as i can get away with no breakfast and no lunch but with tea i have to eat as my mum would realize and she would no as my sister has kind of bin through that. with not eating dinner. and if i did not eat. my sister would blame herself for being like she is to make me like that. and i really dont no what to do. there is no way i can loose weigh so drastically, unless i dont eat. and i wouldnt go not eating for to long. i just dont no how to do it because of my situation. and i dont no a better way. so if anyone could please help. ? Thanks just to let you no i am 121.4 lb and i have a height of 159cm