Your DP won't let you take him back?
Then he had better shift his lazy arse to train and walk the dog.
In the meantime, keep him on an area with hard flooring (eg kitchen- sir out there with him to keep him company) and take him out every hour on the hour for a wee. Also when he wakes up, and when he has had a meal. Stay outside with him until he has done something, and tell him what a clever boy he is.
A reputable breeder will take him back - you may lose a bit of the purchase price because
a) they may have to re-advertise, if they don't have a waiting list
b) they may have to keep the pup for a week or two away from their other dogs in case he has picked up a bug at your home (unlikely, but it can happen, and the breeder won't want any young, unvaccinated puppies being exposed to it)
c) every week older he gets, the less likely someone is to be prepared to pay the full initial price for him. (would you pay full price for a second-hand dog?)
For your peace of mind though, you really do need to re-home this poor little soul asap - the younger he is, the more quickly he will adapt.
I'm not surprised you are finding it hard - hyperemesis is awful, and with some women it lasts the duration of the pregnancy. Even when you have your baby, the dog will be only a year old, energetic and demanding walks, and by the sounds of it, very poorly trained.
There is another poster on this forum who has a dog she detests - the poor thing seems to be stuck in the kitchen/ utility all day, with no company and no exercise and is gradually becoming more and more anxious and depressed. She still wees out of stress, chews things up out of boredom and fear, and can't do a thing right for her owner. The dog is a couple of years old I think, now. We have begged her to re-home her or give her to a breed rescue (another expensive and unusual breed) but she won't - just goes quiet and starts another thread after a while. That poor animal will be slowly losing her mind, and may one day become aggressive because she isn't loved and socialised.
Please don't let this happen to your puppy. Re-home him now while he is young enough to adapt, and to be offered a home quickly before he gets into bad habits. You will all be better for it.