I Have Been Having A Problem Where I Drink More

I have been having a problem where i drink more than 8 glasses of water a day and still constantly feel dehydrated. It has gotten worse over the past week or so where i actually wake up at night to go drink more water. In addition to this i have been urinating less than usual (from 4 times a day to 1-2 times a day) even with increased water consumption. What is the possible cause of this?