Confused!?!

I have been in Brighton since the 24th and when on the first night my sister said to me
" I can see your not eating again" I instantly said "of course i am, i have to eat right, why would you think that, is it cos i didnt have a biscuit before"
she just said " i can tell"
and ever since then nothing else has been said. its really weird cos when i first got over here she wanted to talk to me and find out why and what i was feeling etc but now she jsut seems to get shitty at me. And i constantly feel like this big failure when im around her, like i cant do anything right and she doesnt give a shit about me anymore - im such a waste of space!
I dont know whether to say anything to her or not - what do i say?
"do you think im a failure?"
I dont know if its all in my head or what?!

Yesterday i was going to my friends house and I said that i felt too ugly to go out anywhere and she just said "well dont go" it was said in a real short tone like I DONT CARE kinda mannner! then today we were heading out to watch her husband windsurf and i said is it cold outside and she goes "well you dont have to come"
Its like she really doesnt want me around??!!!

I really miss the way it was when i first arrived - back then it felt like she cared cos she asked me questions and stuff but now its like she has heard it all and there is nothing she can do so whatever.
Its like she has given up caring - given up trying!! :(

But the thing is - i dont really want her to know how much i am struggling at the mo, cos i dont want her to worry - but at the same time it would be kinda nice to have her to talk too - cos she was always really nice :/

am so confused!!