My cat is having a hard time breathing and her pupils are very large what could this be? It is quite cold out side and I haven't seen her around the house and I just found her outside she might have been out for a day or two is she gonna be ok?

That's a great question, although I feel bad for you and your cat.  I would warm her up ASAP.  Wrap her in a soft blanket or if nothing else, make sure she's in a warm room.  See if that helps ease her breathing.  Make sure she's got plenty of clean water close by, too, especially if she usually eats dry food. 

Dry food is probably the worst thing you can feed cats because it keeps them constantly dehydrated.  When cats are dehydrated. Their nasal passages dry out, which makes it hard for them to breathe.  Cold air does the same thing - one reason there are more colds in winter than in summer. 

Contrary to what people think, animals get cold, too.  It troubles me
greatly when I hear, "Oh, don't worry...it's just an animal.  Animals
wear their own coats. They're fine"    My answer is, "Really? Exactly
how warm would a coat of cat hair keep you in 35 degree weather?"

Try to keep her inside when it's cold because sometimes cats aren't very good at taking care of themselves.  My cat wants to go outside even when it's raining. I'll let him out in the garden, but he gets all huffy at me when his feet get wet, like the whole thing is my fault, LOL. 

Anyway, I'd call the vet if she continues to have trouble breathing. It's a good idea to get medical advice from a trained professional. Good luck!