I'm so sorry that your little guy is having this problem

I hope your vet is able to tell you what is wrong with him. It could be very serious and require thousands of dollars in surgery. If it were me, I would have the vet diagnose the problem and if it is a serious congenital defect, I would return the puppy to the breeder. I'm sorry I don't really have any experience with these types of issues, but I know some others on YT will know more. I would be worried about taking a replacement from the same litter if this is a genetic problem, but like I said your vet will be able to tell you more.
Good Luck and I'm really sorry you are going through this.