Ineed (big hugs) Have you ever received any counselling or asked for any specialist help? It sounds as though you have been internalising quite a lot of very negative and destructive feelings and thoughts, and also that you've developed a very negative image of yourself as worthless, disgusting etc.
'For a very young age I was obsessed with sex. If I was groped at school i couldn't say anything I just froze, people used to say I liked it but I didn't know what to do, I froze. So I was an easy target to be felt up by boys and the vicious circle was even deeper.'
Freezing when you were groped is 'normal' given your prior experiences. It's like post-traumatic shock. You revert to feeling helpless and not in control. You physically remember the sensation of being molested against your will. It doesn't make you a slut or disgusting or mean you enjoyed it.
FWIW The same thing happened to me at work when i was in my twenties. A very popular colleague sexually molested me twice. Once when I was alone with him we started talking and then he said I looked stressed and then started to rub my shoulders...and then he groped my breasts. I just froze.
The second time, we were actually surrounded by other colleagues and this time he put his hand up my skirt and into my knickers. Again I could have outed him - I was actually sitting next to someone else. It's unbelievable how confident this guy was. But again I froze while the tears just poured down my face.
Sorry to talk about me. It's very, very hard for me to write this. But I wanted to reassure you that your reaction is completely understandable and common in people who have suffered a previous sexual assault.
You didn't ask for what your brother put you through, you are a special, good person who deserves nothing but good things in her life. You will never be disgusting or worthless. You are not responsible for anything that's happened to you.
(hugs again)