
The simple answer is all these changes may be indicative of pregnancy, but could equally be signs of a phantom.
I have had bitches show very few signs of pregnancy. In fact if my Lexi had not been confirmed in whelp I would not have been certain until a week before they were born and even then I thought it might be a litter of one or two.
A casual observer could not tell she was pregnant at all, and if someone had been of a suspicious nature when visiting the pups might have doubted she was the Mum, as she had very little mammary development other than enlarged nipples, but fed a litter of 7 superbly.
If it wasn't for the post partum coat loss I could have shown her (hypothetically) whilst she was nursing and straight after the pups left, though by 8 weeks after whelp she was practically bald :D
Her mother on the other hand for her first litter ballooned early and was obviously in whelp at four weeks yet had a smallish litter of four, but loads of fluid.