I think this is a common situation. You shouldn't feel so bad about this, because many people struggle with study stress, pressure, and that combined with loneliness. It is kind of a taboo to talk about it.

I looked at your post history and things like loneliness, depression, guilt, self-confidence, self-image keep coming up. Universities usually have student counseling. I would suggest to start there. Once you feel happier, less lonely, your academic performance will go up. All things are connected, so you can get into a negative spiral. But when things are going better, you will get into a positive spiral. Less lonely -> more positive emotions -> better academic results -> more confidence -> less lonely, etc.

I assume you are at the normal age for a student. Your personality is still in flux. If you don't like who you are now, it is not set yet. You can change who you are right now much easier than in 10 years. You can also make friends more easily than in 10 years. So realize you actually have this huge opportunity to work on your current challenges.

It is all about putting yourself outside your comfort zone, failing, being ok with it, learning from the experience, and trying again. That is how people you may look up to did it. Some very cool successful people didn't have smooth high school years. But they challenged themselves during university and changed who they are.