It's Back Again

I was doing fine until recently. I don't know what happened or what triggered it but it's back again. My depression. Nothing wrong is going on in my life and yet I still feel alone and I feel damaged. I feel like there are a million rock just sitting on my chest and there's no possible way of removing them. They just keep getting higher and higher. Heavier and heavier. Like I said though, everything was going great and then last night, BAM! Instant depression hit. I can tell my parents are worried about me. Worried that I might get bad again. Worried that I might try to kill myself again. But it's past the point of wanting to die. I just don't want to exist.