Parents won't let me grow up?

I'm the oldest child of a younger brother who is 15, my brother was born with an extremely rare condition that ended up with having 21 operations. My mom was frequently at the hospital with him during my childhood, I don't think we ever got to fully bond...I'm 17 now, girl and entering my senior year this upcoming fall..however my mom isn't letting me grow up, at all. I'm a good kid, never did anything illegal, always got good grades not a lot of friends, no boyfriend etc...I got my license in December, which I paid most of by myself. I had 3 jobs already, all in which had good reasons to quit (the companies were doing something against the law). I have a goof amount of money to buy my first car but my mom won't let me even talk about it. And whenever I bring it up (I'm a gear head) it ends up in a physical fight, she starts it. My extended family is on my side thankfully, but my mom honestly really doesn't like me...she doesnt care about my well being, my emotions, my friend troubles, my future, grades or mentality...all she does seem to care about is my anxiety and ADHD medication when it needs to be refilled. And whenever she does mention my name she is talking bad about me to her family, friends and co workers. I want to see a therapist, because I have no one that believes in me or wants to be with me. I cant even drive myself anywhere.. So I take my rusty bike and hide my face so no one sees me and I pretend I'm driving a car..it's that pathetic..I need help, I don't want to live with people who don't trust me. I hate myself so much, my mom was right I am a failure.