Water fast

I broke my Water Fast a couple of months ago on day 4 (was intending to do 7) because I was experiencing a couple of symptoms which worried me. Firstly my leg felt heavy and odd, but worse my eyes felt very strange, almost sticky and I couldn't blink well - I woke in the night almost feeling like I had to prise my eyelid open. It was a bit scary and this lasted a few days after I'd finished fasting. Just wondering if anyone else has experienced this on a fast and if this is a common symptom, and how did you relieve it. I am on one Ferrous sulphate (iron) tablet a day. Also, should I be checking my urine for ketone levels? I would like to do a week long fast if possible. Not sure whether to carry on taking the iron tablets whilst fasting or not.