My cat has a hard stomach

My cat had two litters and I got her fixed after the second litter. She was crushed, two never had a chance, and the third died a few week later, and the forth one we were able to save. She morned them for a very long time. It's been a year sense, and now her stomach is huge, and hard. She usually pottys once a day, and drinks a LOT of water. She is very picky about what she eat, unfortunately she eats dry food. I've tried switching her and even making her fresh food. She will not eat it. I worm her, and I have not seen any worms, so I don't think she has worms. I do not let her outside, because we've been having issues with people and their attack dogs...and just people angry driving.... but her being inside never had an issue like this. I'm trying to save up to take her to the vet, I'm just wondering is something that all cats who get fixed after having kittens, that the stomach becomes huge and hard? Or is it some kind of intestinal issue?

Is she pooping? Is it soft or hard?   It could be she's constipated or has hard stools and having difficulty passing them.  Will she eat meat baby food?  You might try giving her some plain meat baby food with some canned pumpkin mixed in (pumpkin puree NOT pumpkin pie filling).

I haven't tried baby food, but I have tried other thing, she is very picky. Her poop is hard, it usually is runny. I was hoping that her no longer having the runs was good. I tried giving her natural things to help her poop, so I'm not sure.

If you want to try natural, you can give her slippery elm bark.  Here's the longest and most informative thread on using SEB.  http://www.thecatsite.com/t/270597/slippery-elm-bark-wet-food-managing-constipation