Vomiting occurs in week three or four after the breeding process. Sometimes, dogs can have morning sickness, but not throw up. This might be the reason why they change their moods.
In the early stages, pregnant dogs feel sick which is why their appetite tends to decrease. In the middle of the pregnancy, they might experience an increase in appetite.
Some dogs will love attention, try to spend a lot of time around their owner, and most likely sleep really close to you. Other dogs tend to get isolated.
Pregnant dogs take all the blankets, toys, and pillows you gave them and make a little nest. They know that this place is a safe place for the whelping process.