My 3-year-old American Bulldog is pregnant with her first litter and I'm excited. This is also my first time having a pregnant dog so I may be paranoid. Some of her nipples seem abnormally large. Not so much saggy yet, but really large and sensitive. I know that her nipples are supposed to get larger but about three or four of them are about the size of a quarter. Is this something I should be worried about?