All I've read tells me that physically it's gone (the drug), but what I really believe is inside your head all those receptors used to getting (for me was a near-constant steady uptake) of nicotine are kind of mis-firing cause they're not getting it. That's the fog and the out of sorts, and the dizziness, and all that other crap...
So even though we're nicotine free, it's gonna take some time before our friggin' brains learn out to operate in that new environment. I think I read on a post somewhere from one of the vets this can be as long as three weeks. Hang tough brother, the fog will lift one day....one other post I read...."it'll suck until it doesn't"....doesn't is coming, wait for it ODAAT like all the rest of us.
In your shoes, man!