why do i bother?

i have had a less than great two weeks.
hannah moved out last week, yelling to dad to fuck off and disowning him, then after her fucking tantrums she moved back in two days later.
dad thinks that i can cope better than she can so he lets her get away with more stuff. like i was crying and i really felt sick and he just said go to school. hannah didn't even pretend to be ill and she said 'daddy, i-i-don't feel very well....' and he let her have the day off.
i haven't slept through stress and crying for two weeks, and on the way home i couldn't even walk properly and i wanted to cry, so som took me home with her and i slept round.
i was so shocked because they didn't accept me and her being together but then let me sleep over! it was so nice to be just doing normal things, no arguments and being with her, i slept so well and she beside me so i felt even better, to wake up and see her face.
but as soon as i got home though today hannah yell at me, and i just think, why do i bother coming home?
i know i haven't explained very well but i just don't have the energy.

am i actually fat?

if i look at myself from mid tummy up i can believe i am pretty sometimes. i have alright hair if i style it for ages, and if i layer the make up i can look ok.
but i have a bump for a tummy and a huge butt and massive thighs.
i have done the dieting and exercising, i can do it in the summer, and i got to the weight i wanted but i cant seem to stick to it. i just put it all back on when something goes wrong...
i go to bed everynight wishing i was anorexic. most people might think that is weird but i wish it so badly.
when i am older i will probably have surgery, but will it make me happy? is it actually my body that is making me unhappy or is my own mind that is telling me the wrong things?