do tets get swollen during first period for a puppy or does this only happen when pregnant?

my puppy is 8 mos old. she surprised us all one morning when we discovered that she had started her 1st period. that was on 4/3 and was around only her dad before that date. he somehow got to her on 4/15 and was sent away on 04/16/. last night i noticed her teets were bigger & each had little hard knots at the area where they meet her body. i don't know if she is pregnant which i never ever wanted until she was at least 1 year old then i was going to spay her. i made sure they were NEVER together.