Why do I feel so miserable

It’s not for any reason I can point out, I spend most of my day dissociated or deeply in focus on one thing, I can’t seem to get things right, have no real friends, and I don’t even know anything about myself. I can’t speak out for myself, hate my voice and want to crush my voice box. Every time I talk, it just feels like I don’t exist and only come back after I’ve finished. Everything feels meaningless and I’ve suffered both identity and existential crises multiple times just this week. I’ve been playing with knives and have scratch SH scars on both hands. I like the taste of blood and laugh at random moments while feeling empty. Why should I keep living like this, I don’t even think I exist in other peoples lives unless it’s convenient for them