Look in the areas where your cat sleeps or sits all the time. If she leaves things like rice particles, she has tape worms. You have to get a pill from your vet for like $5- $8 to get rid of them. It's nothing to worry about. If she has been exposed and is pregnant you will know soon and the above info fromis , so you are all set. Take care. :O)
If her belly is bigger then normal she might be pregnant,if not she might have worms. I would ask a vet just to make sure
1) Do you feed her human food? 2) Do you let her out side to rome free? 3) How big is her belly? Since I don't know these questions I really cannot answer. The best thing I can tell you is to take her to the vet as soon as possible. Hope your cat gets better.
Check the skin around your cats nipples. Usually the hair falls out around the nipples, and shortly before delivery her belly will get pretty tight and firm. If you cannot get her to a vet tonight, then the least you could do is to provide her with a cardboard box and line the bottom of it with a few towels. Put the box in a quiet area like a seldom used room or in the floor of a closet. Make sure she knows where it is. Do not let her out of the house until you can get her to a vet. Good luck to you and your kitty.
There's only one suggestion I could make, and that's to make an appointment to the vets I'm afraid. I firstly would thought would the cats breathing be any to do with it. But, if you sure its not to do with that. There's only the vet option.