Hello I ended up with a prolapse after DD was born but TBH didn't notice anything in late pg. Even if you do have the beginnings of a prolapse (which may or may not be the case for the reasons Bec said) your OBGYN won't do anything about it for several months after the birth as often they resolve themselves. However it's worth mentioning at this stage for the sakes of a) getting some reassurance and b) they might be able to give you some tips with the constipation.