Why do I always feel like I'm in a haze?

For the past 9 months or so I've been feeling like im walking around in a haze. I I feel detached from everything I do, like i'm just watching myself do things. I do things innately but my brain doesn't register that I'm doing them. I just feel detached from the whole word. I don't remember things as well as I used to, and I feel like I can't process or work out problems with the same diligence I used to have. The worst part is I have no idea why. I'ts like i've just woken up and I'm not sure what's going on. I'm 17 years old btw and I'll be a senior next year.