Im a 23 yo dude.
So, i have been feeling worthless for years. I hate myself with a burning passion, feel like i inconvenience everyone around me by just existing. 
I have been bullied a lot, suicidal thoughts started visiting me at the age of 7, by 8 i started harming myself (running into walls head first, scratching and punching myself). 
Thoughts of suicide persisted untill 19, i hate myself to this day.
I feel the need to punish myself for doing something wrong. I don't enjoy it, that's the point of punishment.
Every time that i start actually doing something for myself i stop midway, thinking "who the fuck cares". Started writing a book - deleted it
Started making videos - deleted my channel
Started writing poems in my diary - i burned it.
I started dating and sabotaged every attempt at a relationship, because who wants or needs a piece of garbage like me in their lives
Sometimes i feel like im possessed by something. It's always in the back of my mind. Whispering "you're worthless" "you're nothing" "no one cares about you" "you will die alone" "you have no talent" "just make the world a favor and die already"
Even now, when im more outgoing and cheerful in public and at work, i don't feel the happiness that i show. It's a facade, to blend in. 
My friends and family tell me that I'm just sad, or overthinking it, or just need to stop whining, life is good etc.
Am i just imagining it, or do I have a problem?
I don't know what to think anymore. I feel like i need help, but on the other hand maybe im just doing it for the attention like my parents and peers said.