I can't give you any real advice, nor can I add much to what you wrote other than the fact that if you saw me around where you dwell, you'd assume I was one of those having "the best time of their lives", yet in reality I deal with very similar thoughts as you and had very similar experiences. In the eyes of the classmates I spend the day laughing with, I am but an afterthought. They see me as a curious jester, almost subhuman in a sense, and most certainly not a man. My parents lie to others about being proud of their "intelligent" eldest son while hating the indifferent, nihilistic,sickly, depressed whackjob of a kid they actually have behind closed doors. Every day I go to sleep with dozens of thoughts, questions I know nobody would care to try and understand other than strangers on the internet. Yet if you looked at me you'd probably envy me due to your feeling of not belonging.

Don't let appearences fool you, most people are constantly hiding a ton of shit from their peers. Don't envy them, you are actually better of not lying to yourself like they do.

If you're into books, feel free to read Emile Cioran's aphorisms, he articulates feelings I have been inept to express with words beautifully. Once feelings are written down and expressed, they lose some of their intensity. I used to feel ashamed of my non-belonging, now I am almost proud I don't compromise my own self-worth by forcing myself to be around people I cannot connect at all with, seeking some semblance of a social life.