How can I tell if my puppy is prego?

I have a tinny one year old Coton and shes been acting a little sluggish lately... However Im 36 weeks prego, we moved into a new house, and she is getting more walks 1-4 a day.. (she was an indoor dog for about a year) so I dont know if her mood is changing because of that... She also just got shaved... but I think her nipples and tummy look a little swollen... any help would be great!