Sounds like it to me. I've been having this for the past week or so actually, it's horrible. I have HFA and depression, and at the moment I have a constant feeling that something is, as you say, off. Actually my brain just keeps thinking 'I'm not a real person', and whilst I don't know what that means, it somehow seems to sum up exactly how I feel. It's accompanied with a sense of detachment from my surroundings, and a heavy/tight/hollow feeling in my chest.
I have actually had a couple of brief psychotic episodes to do with derealisation. One time I was in art class at college, doing self-portraiture, and I literally couldn't see my own reflection. I just picked up my stuff and walked out, as calmly as I could; it was horrible. This week I had another: I was walking down my road and all the trees and foliage seemed to go 2d, like in a simulation game where the plants are 2d and they just move with the camera. I felt like all the world was folding in on me, and maybe I was 2d too, and, like I said, somehow not real. I've never told anyone about my psychotic episodes because I don't have anyone to talk to. I just sort of walk them off and internalise them.
If you do have someone to talk to (a doctor even) I would. Derealisation is a very strange and uncomfortable feeling and it can lead into other things (like my episodes above). Even without that though, it's not nice, and I'm sorry you're going through it . Definitely a link to depression, I would say.