Is it normal my brother...

I don't know if this is right or not? But I just need to know how to help myself I have been struggling with this since I was able to figure out something was wrong and I just don't know how to deal with this. Well the real problem is that when I was young my brother would ask me to get naked for him; by young I mean like toddler; he is 3 years older then me and we shared a room. I obliged him at the time because I didn't know any better, well we moved when I was 8 to a bigger house and I got my own room finally and figured out that it was not normal at all and that I disliked this VERY much. My brother took resentment out of me for saying no to him and would lash out and hit me and try to blackmail me into do it but I'd stay strong and never did. Being young though I was impressionable and he would tell me things like ' If I don't let him touch me no one else would because you are ugly and fat' I still never allowed him to see my naked or touch me. But I started to go online and do ''sexual'' things online, I faked people on sites to get men grown men to talk to me and like me and love me, All while my brother still tried to get me to have sex and strip naked for him. I told my mother when I was around 16 about the problem and she didn't believe me when I told her.. And she called me a liar. The only reason my brother came out with the truth on the situation was that my mother threatened to take away a trip he had been wanting to go on. My mother and I had always had blow up fights, she frequently hit me and physically as well as emotionally abused me but never my brother. I still try to talk to my mother about what had happened and how it has affected me but she wont listen she refuses to pay for counseling because she believes there is no ''problem'' she says '' If it was that big of an issue in my life she would of heard it before I was 16'', Like something like this was SO easy to talk to your mother about?