Hi Daiseydoo! I had a really terrible headache for the first 2 days and had to go to bed with it cos I couldnt even see straight. It disappeared on day 3 though so hang on in there.
I drink about 3-4 litres of water a day but the official CD recommendation is about 4 pts a day I think but drink more relative to what you'd usually drink. Hope that helps and your head soon feels back to normal. When you get that first week weight loss under your belt, any amount of pain will have been worth it!!!!