Carb Flu is what everyone goes through after dropping gluten and sugar. It is normal and it takes anywhere from 3 days to 1 month or so depending on the person to get through it. It is your body getting rid of the toxins from the CW lifestyle AND learning how to run itself in ketosis.
Dont worry about working out right now. Give yourself a week off or even two if you need it. Your body has plenty to do with regard to converting your metabolisim to running on ketones instead of glucose. That is what it is doing and it is also why you dont have any energy yet.
Have faith however....once you get through the flu you will have more energy and feel better than you have in a long time! Your body wont have those toxins in it anymore and you will be fully running on ketones (via your body fat and dietary fat). I promise you...it is worth the hell of the flu.
For me, it took about 1 month to get rid of all of my flu symptoms. I had head aches all day, was in a fog, had no energy and didnt work out for the first full week. Week #2 I started to lose the fog and got more energy but I still had cravings to eat carbs (you also need to resist eating carbs or they will prolong your flu). Week#3 I had more energy and no fog anymore, less cravings and less headaches. Week#4.....I felt like a new person. All flu symptoms were gone and I had TONS of energy in my workouts.
So, stick with it. It is worth getting through and changing your life.
If you can just get your....mind together....then come on across to me.....
James Marshall (Jimi)Hendrix