I'm glad you found the info about the "carb flu" online. I was surprised no one mentioned it.
You will feel better soon - by the end of the week at the latest if you stick with it.
I was lucky - I did not get sick when I started - but was prepared by my coach to the point where I almost took the 1st 3 days off from work (I'm a preschool teacher) because I was so afraid of how I would feel.
I would suggest if you are hit this hard in the beginning to carry your salt with you because you might be one of those people that has some dizzy spells going forward as your body adjusts. I did have some dizzy days even though I wasn't sick at the beginning. I found a little lick of the hand, with a sprinkle of salt really helped at those times. Of course it made me think tequilla and lemon would be the next thing.....
It never was......You can do this - It will get better!

the first week is hard as your body is trying to adjust to not having carbs, but soon you wont even crave them!
It's an adjustment to think of getting enough salt, instead of too much, for me at least.
now keep up the good work!