Puppy suddenly stopped peeing outside... and holds pee for a long time
I have a 5 months old puppy. We got him at 2 months, and started potty training him right away. We would bring him outside every couple of hours and he would also sit by the door and whine when he needs to go. He has been behaving pretty consistently, and rarely had any accidents inside.
And a week ago, all of a sudden he just stopped peeing outside, and instead pees in the house. He also started to hold his pee for a long time. Before, he would go every couple of hours, and always first thing in the morning. Now, he would hold it from midnight to some time the next afternoon. We started taking him out numerous times throughout the day telling him to 'go potty', and he just sits there. And sometimes as soon as we bring him back inside, he would pee. So we started to crate him (he's always had a crate, we just use it less often as he became better house trained), leaving him in the crate for half an hour when he doesn't pee outside, and then trying again. But that hasn't helped. He just whines a lot more to be let out.
I know he wants to pee, because after holding it for so long, he pees for a loooong time. And when we take him out for walks, he would sometimes go a couple of times in an hour. But for some reason, he just refuses to pee in the backyard.
I have no idea why he's doing this all of a sudden, and don't know what to try to correct it.
Any ideas would be greatly appreciated at this point.
Thanks.