I am by no means an expert but 'low carb flu' is normal. How many carbs are you eating a day? You might try adding more in the form of sweet potatoes, higher carb veggies, berries, etc and see if that helps. Sometimes you have to taper yourself off. I have heard some people complain of the thirst. I am type II diabetic and just recently added in more carbs due to energy loss. I found for me it started a horrible sugar craving. I am weeding them back out. If you could share what you are eating it might help to to give some ideas of what if anything needs to be changed.
Don't give up!
You know all those things you wanted to do: You should go do them.
SW 215 lbs
CW 180 lbs (whole foods/primal eating)
LW 172 lbs
GW 125ish lbs