could kitty be pregnant?

[smg680]

In my dad's garage, we have several feral cats who have adopted us. Not too long ago, Dad and I took four of them to the Humane Society to be fixed, since two of them (Cutie Pie and Little Mama) have each had two litters of kittens. There are at least 15 total cats in our garage. We also took the (as far as I can tell) only male 'Horny Bob' in with us too, to avoid any more litters with the other kitties. They are back with their friends and extended family, and they are all doing very well. (I say 'as far as I can tell' since I'm not sure how to tell the difference between male and female cats when they're young; after all, Ambre was Amber until the vet proved me wrong! And we have another feral cat named Lily, who turned out to be Leroy!) I'm not sure which kitties are male, and which are female. How can I tell which cats are male, or female?

Getting back to the question at hand, how can I tell if a young cat is pregnant? We have a gray and white kitty (whom I call Kitty-to-be-named-later), who I think looks like she could be pregnant, even though Bob has been fixed. She looks young, but I thought I saw that her belly looks a little big. I've seen Cutie Pie and Little Mama when they were expecting, and Kitty-to-be-named-later is not as big as they were yet.