Life feels fake

I don't know how to describe it, but I've always really felt this way. It feels like life is fake. Like I'm a dream. Like nothing I do matters because it isn't real. Like everything is an illusion and it isn't worth it. It's getting to me. I don't know what this is. I can't make rational decisions because I don't feel like I'm a real person, I feel like I'm part of a story someone's writing or something. It really is how I truly feel. Everyone and everything to me is a dream. Has anyone else ever felt like this? It's scaring me, honestly. Ive also been dealing with depression, self harm and suicidal thoughts for a few months. I really don't see the point in living an illusion. I'm kinda lost here. Thank you for any help, I need it.
(FYI- I am an athiest and cannot turn to a religion.)