My cat was last in heat in mid-July she has not been since.
I think she’s with kittens but I do not think I can feel them as I could with the other female cat I have.
Is she pregnant with kittens or is it something she thinks?
It is not always, you can feel or see it on the stomach if your cat is pregnant.
As far as my calculator can calculate, she is also only in the third-fourth week, if she is mated in the maturity, you have observed, and often you do not start to be able to see an increased range before around the middle of pregnancy, ie. fourth-fifth week.
In return, there is another sign, you should be able to see now: the teats get bigger and redder. If they are not, she is probably not pregnant.
A cat can easily become pregnant, ie. think she is pregnant without being so, and show all signs of pregnancy.
But a s.k. “Empty pairing”, ie. a mating, which does not happen, can also give a kind of “birth control pill effect”, without the cat becoming pregnant.