What would you want instead? I also don't want marriage and kids...

Honestly, I felt very similar to you in 12th grade. I honestly thought I was going to kill myself by the time I was 20, and only applied to colleges because it was expected of me and my peers. Then I did disastrously bad my first two years of college. Let me tell you--it's not the end of the world. Very few things mean the end of the world. I'm a few years older than you, and still struggle with finding meaning, or a reason. But sometimes it's okay to just go through the motions, while realizing that we don't know what we want, to just keep going while we find something we do want. Hang in there. I am sure there is space in the world for what you want even if it's not traditional.