Getting a dog to use pads

I got a three year old chihuahua. He's house trained. I take him out to pee about every three hours. However he has managed to shite in my closet twice, so that's one reason I'd like him to use the pads. He doesn't have any way of telling me he needs or wants to go out or he doesn't know how. Well, he will stand in front of the patio door to be let out but he doesn't relieve himself out there

Also, I went to work today and put him in my bathroom, with his food and water and blanket. He freaked the frick out when I got back, even though I was only gone three hours. I don't know if he was freaked out about being trapped or what. But I feel like I need to leave a pee pad in there too for when I'm gone all day

I just put one down on the patio and tried to get him to check it out but he wouldn't go near it. It's some kind of puppy potty training pads that are supposed to attract them