How to tell if shes pregnant?


Hey guys. Me again. So not about my pregnancy but possibly my dogs.. i got her a week ago and the lady said she got out of heat a few days prior (okay so we are looking at 1.5 to 2 weeks ago according to her). This little girl is 1 and was indeed around other dogs who were also not fixed. She is lazy and tired. She sleeps all day and plays for maybe a few min at a time. Her nipples are large and boobs are swollen, and she hardly wants to eat. I plan on calling the vet on monday but they're closed all weekend. This is my first dog so i dont have experience. Does anyone have any tips on how to tell if she is pregnant or not ? I read that i cant wait for a bump to show up because that happens later in pregnancy for dogs.. i dont have any of this pups medical history or anything so idk whats happening. All she does is sleep!