Possibly pregnant 9 mo Olde English Bulldogge

Question
Well it seemed our pup was in heat forever.  We caught a Golden Retriever in our yard.  The vet said it isn't likely that she got pregnant because of the size differnce and there was a mess on her back.  How do we know?  Do we have to wait 30 days for an ultrasound?  Also her nipples are big.  What do you think?
Thank you

Answer
What I think is that you should have been more responsible when your dog was in heat and not allowed her outside unsupervised until you were sure the cycle was over.

Too late now.  All you can do is wait. Her nipples are probably just enlarged a bit from being in heat. It would be too early to tell if she's pregnant strictly by this.