Not pregnant but pee a lot!

I was wondering if any if you ladies had the same problem, I drink 61oz of water a day because of my weight, physical activity, etc. I drink a cup every 1hr and 30minutes because if I drink more I pee even more, my bladder has a maximum capacity of 1/2 cup, yeah I've measured it.. and I can't seem to hydrate myself, I'm tired all day, weak, no saliva, heart(blood pressure) races with any effort(house cleaning, taking a shower, etc.) And of course it's because dehydration.. but I don't sweat so my dehydration has to be because of my "excessive" urine output.. I pee about 4 times per hr on average so I been told that my uterus could be tilted and putting pressure on my bladder, because my bladder capacity has diminished dramatically over this past 4 years! Mabye my kidneys can't absorb "all that water" either, any thoughts, opinions, advices! Thanks!