Take it easy on yourself. When adapting to a normal human diet (that is, one not swimming with simple carbohyrates) there's an adaptation period. Try upping your salt intake if you like (Volek and Phinney recommend this) to lessen "low carb flu." Also they recommend backing off a bit on exercise during the first coupel weeks and then adding activity back in. Drink more water.
I drank a cup or two of chicken broth (I used Knorr, best tasting) a day when adapting and it reallyhelped.