how can you tell if a 22 month old cat is pregnant?

The obvious answer is bring her to the vet for a physical exam and perhaps an ultrasound. Regardless I suggest heading to the vet because if she is acting like it is painful to touch her sides and/or belly she could have other problems going on. I can prognose till I'm blue in the face with many abdominal problems, but bottom line take her to the vet for an exam, if nothing but for peace of mind and a clean bill of health and perhaps discuss with your vet about spaying. :)

A simple (but non-informative) answer would be to wait about 9 weeks and see if she has kittens! But you are asking "how can you tell...if a cat is pregnant". Some things to look for would include: "pinking" of the nipples; abdominal swelling; increased appetite; increased affection. IF your cat had the opportunity to be around a "tom", there is a high probability that she is pregnant (due to nature and the "spontaneous ovulation" that Doc Jill pointed out).

How can you tell that your cat is NOT pregnant? Have her spayed!

Doc Jill, I am so glad you posted that. I never knew that about cats. I know of a few folks I am going to pass that info to in hopes they will curb their furball litters coming every few months it seems. That certainly needs to be more widely known. God, I am glad humans aren't made that way!!!

if she isn't spayed and she was outside for more than one second, she's probably pregnant. Cats are spontaneous ovulators, which means that when they mate, they automatically ovulate, so its almost a guarantee that they get pregnant. No wonder there are so many kittens/cats, huh! Get her spayed and you won't have to worry.

Most cats love getting their bellies rubbed even when they are pregnant. Maybe she's just touchy or maybe she has some other problem. It wouldn't hurt to take her to the vet and if she's OK it would be a good time to have her spayed.