Ive had the same problem with drinking tons of water but feeling on the edge of dehydration. I took an ambulance ride to the hospital because I was passing out and they said I was dehydrated.

So I upped the amount of water I was drinking to nearly 2 gal a day. I told my doc and she said it was too much so I cut back a little. A few days later I thought I was dying again and went to the hospital and they treated me for dehydration.

I tried drinking drinks with electrolytes but in all honesty I didn't see much of a difference. I was skeptical that it really was dehydration due to how much I was drinking but the docs said the dehydration was likely from all the meds I'm on which is the most likely explanation.

One thing I found that's really helped is stopping all caffeine and diet drinks. Coffee is a diuretic and for some reason artificial sweeteners hit me hard. They chap my lips, make my fingertips shrivel and feel dry, and make me feel extremely thirsty. And Adderall made me fiend for water.

I keep a water container on me at all time when I go out with a spare gallon in the car just in case.