On my second attempt at cleaning up which was just over 3 years ago to feel totally normal it took me a good 3 months, but then my drug was heroin. I think the first 2 weeks were the worst, I would have done anything just to get a good nights sleep also I suffered with hot and cold flushes not nice in the middle of a cold winter and the stomach pangs, throwing up went roughly by week 4.
I'm cleaning up now and I'm on my 2nd month off opiates come March the 13th, I still get random hot and cold flushes and just recently my stomach has been playing up and once in a while I get a very anxoius flighty feeling, sadly the urge to use again still lingers I really wind myself up just by thinking about the stuff =/
Well 8 days is great, just keep going taking each day as it comes by next week you will feel much better, scheming and thinking about it just makes things worse, divert your thoughts, meditation is something that will help a great deal. Good luck and are you on any treatment?