I had this at the beginning quite a lot - I have low blood pressure and thought it may have been that but others on here have also suffered similar lightheadedness. Maybe it is a case of your body getting used to full nutrition and less calories.
Also you have drunk a heck of a lot of water, maybe it is a little too much?!?
Thanks for all your replies.
I have spaced out the water throughout the day but did have coffee earlier which may have given me a caffeine kick. My counsellor told me to drink 6 litres so I have been doing that and probably more. My blood pressure the other day was 133 over 90. I do feel better after having my 4th pack. I just did not like the feeling. I felt out of control as if I had had 2-3 glasses of wine. Really woozy. I hope that I do not get this feeling too often. Thanks to everyone for being there.