How to tell if your cat is pregnant?

When i moved I had a female stray cat show up. I have a male outside cat..... I've noticed her belly is enlarged, and she's being affectionate to me, but when I felt her they were "perky" but not enlarged. I tried to feel her belly, but she was moving around too much to really feel for lumps. I've been thru dog pregnancy, is cat pregnancy like that??