How do I break my pom from peeing and pooping in my house?

My fiance bought me my pom about a little over a year ago, he is now a year and a half. When he got my pom, Maverick, he was potty trained. Now he did still have some accidents but only recently has he gotten really bad about going in the house. I do have a Corgi who is 7 years old and neutered and he has never gone in the house. Maverick will go outside with me and my corgi on a leash and will pee one or two times. He then seems to get distracted and its like he forgets to finish. I let him stay out for at least 5 mins when I know he needs to or should have to poop but he still won't do it. I have tried the routine of bringing him in and putting him in his cage for 15 to 20 mins then taking him back out but all this seemed to do was train him to go to his cage when he comes in from outside no matter what. When he does poop inside it's not immediately when he comes inside it's more like he goes when he feels like it.

He has told me sort of speak a couple times that he needs to go back out but won't do this all the time. He will also pee all over the house, he has even gone as far as raising his leg on our brand new couch no smell of dog anywhere on it. I'm not sure what's going on with him. I have had several dogs and never had such a problem training them. Maverick is not neutered but I want to avoid that because we are looking to breed him. This has been going on for several weeks if not months. It's really getting frustrating. Is there anything anyone can suggest so we can break him of this behavior? One more thing my fiance got a new job and he is gone 4 to 5 days a week. Maverick has strong bond with him, would this have anything to do with his behavior ?