Hi now that her pregnancy is this far on the pups are in the rapid growth stage and they are pressing against internal organs her breathing will be quiet heavy sometimes you will find she breathes better when she has her mouth open a little like panting.
Do you have an idea of how many she is carrying.
Now is the time to give her small meals a day rather than large meals her normal daily food intake needs to be increased.
Sure someone with more advice will be able to help as they are full of knowlegde on these boards.