You don't need a reality check, except for maybe to be so much kinder to yourself than you are. :(
Listen, you're in your last of high school, in a time that is all kinds of messed up, and adults don't know what they're doing, so why would you?
You're also at a point in your life where you are trying to figure out what to do next, as if at 17/18, you're supposed to know this. I can promise you that I did not. Sometimes, people know early, and others need more time.
I don't know how your brother is different than you, but you aren't supposed to be the same as him. You just be you, and let him do his thing. You are worth loving just because you are you, and not because of things you do, or accomplish.
I don't know a single person who has succeeded at anything without relying on someone. Are your parents telling you not to rely on anyone, or is this something you are telling yourself?
Your parents job is to raise you to adulthood and to make sure you are equipped to do the best you can. This means making sure you are clothed, fed, educated, taken care of when you are sick, etc. It means they try to teach you how to set and reach goals, be able to manage socially - stuff like that. It means they love you, and make sure you are safe. Some of this includes rules and discipline.
It does not mean that they get to tell you what you are supposed to do when you are an adult, what career to enter, or make you feel unworthy. I don't know if that's something they are doing, or something you are doing to yourself.
I'm not a mental health professional, so I can't tell you if you have depression. I'd say it's certainly possible, and I think you need to tell someone who can help. Is there a teacher, counselor at school, the school nurse or clinic worker you can tell? Maybe your school has a social worker? Maybe another trusted adult, like an aunt or uncle?
What you do and accomplish doesn't make you lovable. Just being you does. I hope you talk to someone.
When you say you feel like dying, if you are having suicidal thoughts at all, please text Home to 741741. That's the Crisis Text Line, and you can text with a trained counselor.
Please just be kind to yourself. :)
Your first line was, you have no mental health problems, and then you describe a litany of mental health problems. Talk to your parents about what's going on and consider seeing a psychologist to learn why you are so incredibly hard on yourself. It's not a fun way to live, is it?