There is a spray that you can buy that is Doggie No and other names. it is a repellant, You could try spraying it near your door to bedroom. But, dog needs to be fixed asap if not. The other thing I thought is that he is pissed off with you for leaving. I have had dogs pee on my bed, it's a pain in the neck and they need to learn it quickly. Mine did grow out of it. I have to say neutering is very necessary with this issue.