The possibility of getting alzheimers from weed worries me too, there's really been no study's on it that I've heard of. all I can say is the brain attrophede's and has greater chance of alzheimers from lack of use, which is why they say you'll have a considerably lower risk if you read a lot, learn instruments, etc.

but, from the sounds of it you're just permafried, as I have been at times too. just go off for about a week, and about 3-4 days into that week you should be back to normal. however, I know how hard it can be when you've become accustomed to smoking every day.