I am sorry to hear that Callie has deep, labored breathing, is lethargic and has cried out as if in pain today.
A normal cat has a resting respiratory rate of about 10 to 15 breaths per minute, and one breath is considered the in and out motion of his chest. If she has a rate faster then 40 breaths per minute then she is in trouble.
If you can notice that she is breathing abnormally then I am concerned for her.
If she doesn't have a nasal discharge and isn't sneezing then her difficulty breathing is likely related to a problem in her chest or secondary to anemia (decreased numbers of red blood cells).
Problems in her chest leading to an increased respiratory include primary heart disease (including cardiomyopathy and heartworm), lung disease including asthma, bacterial, viral, parasitic (lungworm) or fungal infections, a mass(es) in the chest including lymphoma, heart based tumors or carcinomas, or fluid around the lungs (pleural effusion) due to a mass, bleeding, chylothorax or an infection.
Given that she sees cold and her gums seem pale I suspect that anemia of some sort is part of her problem, although we cannot fully rule out heart disease.
Anemia can be secondary to poor red blood cell production, either due to kidney disease as the kidneys make a hormone to stimulate production or primary bone marrow disease, or anemia can be due to bleeding or destruction of red cells due to a tumor, blood parasite or autoimmune disease (body attacks its own red blood cells and destroys them).
If your girl's tongue and gum color are a very pale pink, white, blue or gray, these would signify she is real trouble and this is a true emergency.
The conditions I listed above are serious and I would highly recommend that your girl see a veterinarian promptly to have an examination and further testing done based upon her examination. Callie likely needs radiographs of her chest to evaluate her heart and lungs, a complete blood count and possibly an ultrasound of her abdomen to look for abdominal bleeding to start and then further diagnostics based upon those findings. That may include testing for heartworm and lungworms, aspirating fluid for examination if there is fluid present around her lungs, or blood titers for fungal infections.
In the meantime keep her quiet so she can breathe as easily as possible.
Please let me know if you have any further questions.