Senior dog peeing in the house

My dog is a 14 year old male neutered cavachon, and for the past year or so he has started peeing in the house, despite the fact he is potty trained.

I let him outside pretty much every hour of the day, and he usually wakes me up to go in the middle of the night. Anytime he wants to go outside, I let him.

It’s not incontinence since he is intentional about where he is peeing, and likes to mark items on the floor. He is healthy and has no joint issues or a uti.

I can’t keep up with it anymore and am thinking of putting him in diapers which I really didn’t wanna have to do.

Any advice would be helpful.