Hiya, what do you do to him when he does this? Are you doing any training with him? Does he know his place in the "pack"? Do you practice NILIF with him? Sorry for the questions, just trying to get a better picture
Also one very basic rule I follow with any pets, is that if there are places, items, shoes, etc that you don't want him/her to get at, then you must keep them out of reach. That means keeping your doors SHUT to pup at all times. Don't even let him on the bed, even when he isn't pooing or weeing.
Has he got a place to call his own? A crate, or bed for example? He is still a baby, and needs to be taught these things. Limit his movements throughout the house, until he has learnt some training and manners. That means beds, bedrooms are all "No Go" zones for him. Go back to basics with his toilet training, until you have taught him that outside is the appropriate place for toileting.
Is he displaying any other undesirable behaviours? Does he get excercise and games? There are plenty of places in my house that the pets know they aren't supposed to be in. Bedrooms are one of them unless it's night time, and both dogs sleep in the bedroom. My cat sleeps in the laundry at night and has water, his tray and his comfy basket
It doesn't take them long to learn the boundaries as long as we teach them to them effectively, with gentle training methods, and lots of love and praise
Once again sorry for all the questions, it just helps to get a as much as information as possible
good luck and by the way we love pics here heheh any pics of your baby?