Toilet Issues for New Guineas

Question
I am a new owner, I've had two female guineas for 3 weeks today.  I hear other owners online say that they go to the bathroom in one corner of the cage, but my two are still going all over the place.  Is this normal?  Should I be doing anything to assist them in finding a place in the cage to use as a toilet?  When I change the cage I leave a small amount of old bedding in the corners so that it will keep their scent, but they are just as likely to go there as anywhere else.  Also...I think one of them might be pregnant.  She got really fat this week and is lopsided.  Plus she has started nipping the other guinea anytime she gets near food or near her.  Could this have to do with her going all over the place?  Any advice would be welcomed.
Thanks a lot!

Answer
Hi Melanie

Usually piggies do use one corner as a toilet but this mightly only happen after they have got fully used to their cage. Don't worry at all about this.

From what you say your other piggy is pregnant but the only way to be sure is to weigh her on a daily basis for 2 weeks and see if there is any substantial weight gain.

Andy