If im off work in gaming mode, sometimes I forget to drink for a few hours, and notice I have a light-head when I stand up, or I'll get symptoms of a migraine. But for the most part, I generally drink 2 bottles of water (600ml) 2-3 glasses of orange juice, and at least 2 cups of coffee a day.
I'd like to quote a site I found earlier when I googled "how much water is too much"
"Your kidneys must work overtime to filter excess water out of your blood circulatory system. Your kidneys are not the equivalent of a pair of plumbing pipes whereby the more water you flush through your kidneys, the cleaner they become; rather, the filtration system that exists in your kidneys is composed in part by a series of specialized capillary beds called glomeruli. Your glomeruli can get damaged by unnecessary wear and tear over time, and drowning your system with large amounts of water is one of many potential causes of said damage"
OP, I think it would be wise to you see a doctor about the excess amounts of water you're consuming daily, as it may be a early warning about diabetes.