Since you are limiting your number of drinks a day, your electrolytes might be getting out of balance. The lemonade provides those and if you drink only water, you can leach them out of your body. I have an arrythmia and when I tried a water fast, I found myself in the er they were so bad. My dr just told me that too much water isn't good for you either. Maybe if you just up the lemonade a little it will take care of itself. I can't remember what the name of the condition is for too much water, but I do know that headaches are a major symptom. Hope this helps