My dog coughs all the time, she is short of breath, and I believe she has too much phleme.

Your dog may have kennel cough. Please take to the vets to be sure. This is not a cough like humans get and can prove to be fatal if left untreated. Do not give your dog human cough medicine.

NO NO NO, do not give your dog cough medicine!!

As Twinkie said Kennel Cough is the first thing that comes to mind.

What breed is it and how old?
This can also have an effect on their breathing.