Hi, I am Dr. Peter and would like to help.
1- How long has this been going on?
2- Take a look at her gums and see if they are pink like yours or pale?
4- Vomiting or diarrhea?
1- How much does she weigh?
2- Did these symptoms come on quickly?
3- Has she been slowing down gradually?
4- Is she having a difficult time going up steps or getting up from the floor?
When a dog breath in this manner it can be related to pain, primary cardiopulmonary disease and even a fever. Her not wanting to walk could be related to either heart/lung disease or neuromuscular (bad back). This case needs a hands on exam by a veterinarian immediately. If you have access to ER vet you should consider having her checked, if this is a heart problem it is best treated early. If you do not have access to ER vet, keep her quiet and do not attempt to make her walk. Allow her to move when she wants too. Do not give anymore Benadryl, ok to give her aspirin every 12 hours. There is not much more you can do at home. Follow up in the morning with your veterinarian.
If you have additional questions I will be glad to answer them.