My female cat mocha has been fixed for over 2yrs. But we got a male cat who was not fixed and as of a month ago she started not letting him around her and her tummy is getting big, I've cut back there food so they are not over eating and she sleeps a lot more than she use to.Im finding different answer for this uestion I just want to know for sure.

You can't really spay a cat 'wrong.' the process involves removing all the reproductive organs. I can't see how anyone could do that wrong.

It's possible that he's trying to mount her and she finds it annoying.

How old is she? Cats can hit a middle age spread, just like humans. I've seen cats hit about 5-7 years and suddenly put on weight and be a little fuller around the middle.