I have similar concerns with my 11 month old Yorkie. She is small weighing only 2 lbs 11 oz. This is her first heat cycle and 2 weeks into it she woke me at 5:00 am. whimpering and crying like she was in pain. Prior to this the only signs were the swelling and slight bloody discharge. She romped and played as usual. My first reaction was to take her to the vet, which I did and after checking her, it was determined she must have pulled a muscle in her back from jumping off the bed. I still am not satisfied that this is the case just from observing her actions throughout the rest of the day. A chortizone shot and muscle relaxers have helped, but I wonder if her pain could be due to the heat cycle.
