It is the SB flu don't worry it passes in a few days. It is your body's natural reaction to "detoxing" from what we "used" to fuel ourselves with. VERY common. Just hang in there it will pass. Have herbal tea or coffee it helped me....oh and sneak in a nap if you can.
Beans and dairy are also supposed to help with the SBD flu.
I gave myself permission on P1 to take it a little bit easier than usual....go to bed early...It really helped me get through because there were times that I felt just plain ol tired. I seem to remember day 11 I was exhausted.