I sometimes feel that my existence is pointless, I try hard to make my parents proud?

Hi I'm 14 but super mature for my age. I feel as though I just don't care about anything I have plenty of friends but still crave attention, often times I get angry or jealous of them. I have yet to feel as though I truly love something, this makes me a very bad decision maker. I am the middle child as well, which is okay. My parents excpect so much from me, considering how immature my older brother is. He makes his bed and gets a standing ovation hes lazzzy and 17 they should excpect more from him. My sister is younger but everyone sees her as this sweet angel, she is complete evil. She often threayens me, throws things at me, there was a time when I feared for my life. If any of them get hurt t a big deal gets made about it. When I fall or am sick I tend to keep it to myself, I don't want to burden my parents and I usually figure out a solution myself. I have a 4.0 GPA always get A's yet I feel like to my parents they don't really care, they simply excpect it. But when my siblings do it they make a big deal out of it(which is every report card pretty much) I am also a skater, I've competed a few times but just havent had luck with it-my mom always tell me to improve never is satisfied with what Ido. I want to win competitions to make her proud but I simply can't. My sister on the other hand comes out with 3rd or something to that degree. Idk what to do I just want to be happy without letting anyone down. I just want to find a solution. Im not unhapp all the time, but alot of the times I just feel like my friends woulf rther bewith someone else or my parents would be better off without me.