I dont know much but I know one of the first signs I noticed when I thought I might of had a pregnant cat was her nipples went big and pink I believe that starts to happen either 3 weeks after she becomes pregant but Im not sure, thats defintley a big clue though of course there is that her belly gets large but I wouldnt automatically assume if her belly blows up she is pregnant because I think it can be from worms aswell, or she is just getting overfed. A vet visit is a really good way of telling if she is pregnant but sometimes they cost ridiculous amounts just to tell you she is or isnt pregnant.When they are getting closer to giving birth you can usually feel them wriggling around but not always.To be perfectly honest with the cat i talked about before i was never really sure whether she was pregnant or not untill she had 2 kittens one day!
If you haven't already, this might be a good time to review the information contained here so that you can be prepared in the event your cat is pregnant.
Well, of course, you sort of have to wait. Her belly will eventually get bigger. Her appetite will increase, and things like that. The vet is an option, but it would be alot cheaper to wait and see what happens.