I Feel Numb

I don't want to do anything anymore... people invite me out and I decline and say I have a lot of stuff to do or have other plans, when really I just stay in my room, I don't feel like eating or anything. What does it all matter anyway... no one cares anymore. I don't talk to anyone anymore, I just ignore everyone and feel bad about it but at the same time why should I? I just want to disappear