Sibling bias

ever since I was little, my parent has always favored one of my siblings. Until I grew up to be a teenager, I didn’t mind, but as of today (I am almost 18) I noticed the bias that my mom takes. Whenever a fight breaks out between the two of us, my mother has already decided to take the side of my sibling without hearing my side of the story. This has happened so much that I began to make a list. Each and every time that we fight, my mom never stood up for me, and she ends up hitting me while my sibling stands there laughing. My mother also likes to tell me to listen to my sibling because they’re older, yet I’m always the one who doesn’t hit back when they hit me. My sibling never takes their role. Adding on to the chaos, I have brought this to my mothers attention, but she blows it off and refuses to listen to me. So I am deciding to never talk to her about my problems ever again. I feel like they just use me to clean and cook but don’t really care about my well-being. I want to defend myself but it always backfires on me and leads to yelling and the same cycle over again. Also, whenever little things bother me that my sibling does, I keep it to myself because I don’t want the vibe to be bad. But, whenever a minor inconvenience happens that I make, my sibling likes to take things from 0-1000. It’s not fair since I like to keep problems to myself... and when I give them the same treatment I’m in the wrong and they’re the victim. I took my own advice by keeping quiet but I’m sick and tired of it. What should I do?