My dog is 16 years old, he never went in the house> He always goes to the door and barked to go out, and still does. He'll go out and then come in a go poop in the house. This started in the summer. Its like he doesn't even know he's going.

It's his age; he's losing control. It's very common. Get some poop and pee pads (or just incontinence pads for people) for all over the house.