why can't my parents understand that I love them but I'm old enough to make my own decisions and…

why can't my parents understand that I love them but I'm old enough to make my own decisions and choices instead of making me feel like I never do anything right but yet my 19 yr old brother has no job lives at home with his gf an wears 200$ shoes with a $700 Xbox but when I leave to do better I go contradiction an do whatever you want to do comments like seriously I definitely want a better relationship with my mom an family but they just don't get me at times an the fact that I suffer from anxiety an bipolar disorder doesn't help it's shrugged off as she's just acting crazy but yet when my brother acts like a spoiled brat and do dumb shit it's OMG is he OK?!!? I swear my life could be a sitcom SMH