I have to say that the first week is - by far- the worst. Closely followed by the the second!
However once I got to week 3 it was plain sailing for me. I felt very good, I was getting the best sleep I'd ever had, I had tons of energy and best of all I was losing weight - and losing it quickly.
Please stick with it cos the results really are worthwhile.
As for the headaches - drink more water and they will be gone in the next day or so.
I'm on day 15 now and no longer feel hungry and haven't had the headaches for a week Keep going you will feel better soon - try some painkillers for the headaches and drink loads of water.
day 4 was my absolute worst and by day 6 I was home and dry and high as a kite from the ketosis and weight loss. hang in there, that headache will be gone soon. keep downing the pints (of water of course )