American staffordshire terrier pregnancy

Question
How can I tell if my dog is pregnant? We adopted an amstaff about 5 weeks ago. When we got her, her nipples were large and the same with her vulva. Her rib cage is getting larger she is eating more and more everyday but her ribs and her backbone are still showing. Her belly is hanging low and is not filling in. We have had other people say that she is pregnant, but we are not sure. If she is pregnant what do we need to do to prepare for the pregnancy? She is becoming lazy a lot faster then when we got her. We want the best for her but can't afford a doctor bill on a chance.
On another note how can I stop her from eating cat poop?

Answer
I was trying to answer you and my computer crashed.  I would supplement her food with some cottage cheese to add some calcium to her diet until you know for sure.  There is no sure way to tell, she does have all the signs though, so you may end up with a litter.   Increase her food so she gets filled out.  Make sure she has no discharge from her vulva and that she is urinating ok.  If you see a green or black/brown  discharge she will need to go to the vet RIGHT AWAY or you will lose her.

All dogs eat cat poop....Put the litter box behind a gate so the cats can get to it and the dog cant...with her eating that stuff she and pups will need early worming
nancy