Why do i feel like i dont exist and that im not really here or alive?

Obviously, you do exist, are alive, and I doubt you're being philosophical here as in; is this all a dream? I suspect you need human feedback and interaction, i.e. you're lonely and feel unappreciated which can be depressing. The solution is to seek human contact not from those already around you but somewhere new. Professional help maybe, but it doesn't have to be. Find someone to talk to.