It does take time to adjust to this diet and everyone is so different. I had so many weird symptoms at the start it was easy to blame everything on the diet. In many ways it was body saying - umm excuse me where are my usual calories, alcohol and treats'?
In my experience it sort of settles down as you get used to it. When in doubt drink more water, that always helps. Take an early night, that seemed to help too at first. Its an unknown journey and changes like this can be frightening - but as the body gets used to the idea of three magic packets it does seem to settle down. If you are ill, seek advice, or just hang on.
If it helps, once I had got the hang of it I never felt better... as the weight dropped off I felt increasingly better each day, the energy is amazing, so many bits that used to ache just don't any more. Its a delight to put down a five stone suitcase - I used to take it everywhere!
GSQ