This sounds like a simple case of low self esteem. I know its not really that simple, because I can really relate to it. Really when you think people might notice and label you, it doesn't matter! Some people just dont know a nice person if they came and bit them on the hand- nice people dont do that so they just wont know! Most people are into themselves- what we percieve has to go thru our own filter- so everyone really thinks too much of themselves.
Here are some thoughts anyways,
Your sister is one of the only people you are equal with- she knows you and loves you unconditionally.
The pavillion could be a place to put all your fears about yourself and general fears and dislikes, the sick people you dont want to be a part of.
The sick people are those you associated yourself with, they are the losers in this world of ego's and materialism, snotty beautiful cold people who dont care for what does not please them to the naked eye. Very Judgmental.
I think you are not that way at all, but feel that way sometimes.
We all feel like that sometimes! Even movie stars hate themselves while others love them! NO one is perfect, and a lot of people hate crowds.