Yup that is all right and they are all different with the milk part and teats swelling. Just the other day I was around a chihuahua for 4 days before she gave birth and she didnt produce milk nor did her teats swell until the first pup was born. The only way I knew she was REALLY close was with the nesting, panting, restlessness and her temperature dropped to 98 degrees. She got false contractions the day before which were not as strong as the REAL thing, I read that it is when the pups are getting in their places. I had purchased a book on breeding which I didn't let go during the birth of the pups. "The Complete Book Of Dog Breeding," By Dan Rice, D.V.M. Excellent book with alot of info.
