Why do i feel so dead?

i feel like nothing matters or has a point to it. I really hate how nobody likes me and i have no friends and everybody else does and is always hanging out with people or texting them or something. I always feel so lonely and deserted because nobody ever wants anything to do with me. I was really depressed for about two months and stuff, i self-harmed a little to block out all the pain and i almost killed myself. But those feeling went away about a week ago and now i feel numb. Its happened before ill go and feel numb for 2 weeks or two months and then i go back into being depressed and it only gets worse. golly i hate feeling so dead