I need more information. When you write you take him out potty - do you just let him outside or do you leash walk him or what? Also when does he eat his last meal? One more question - what do you feed him?

He eats Natural Balance Food. His food is put out in the morning, he eats bits and pieces throughout the day, then eats the rest at night for some reason. He is walked on a leash for about 45 minutes every day around 6-7PM. He is taken outside on the leash to pee at around 10 before bed.

jockewing, stop giving him water and take him out again. Or have a tie out for the late night potties, watch him from the door and when he goes, praise him and tell him night night time (or whatever your key word is for bed).

Scratching doors says he wants outs out again, not water.

Because this changed in just the last few weeks think about what else might have changed around the same time.

It might be something as simple as Daylight Savings Time if you live in an area that has it. I am convinced that dogs have internal clocks based on the sun. Then their humans go and change the clock twice a year.

i know you said he got a recent clean bill of health but it's possible he could have developed a UTI between then and now. i'd start with getting a catch of urine and having it analyzed by your vet to see if there might be an bladder or kidney infection going on.