I took my cat Patches to the vet to take a look at some things I figured could be a problem.
I told the vet that her stomach seems rather hard and stiff, rather than soft and plump like a cats belly should be. The vet diagnosed her with a bladder infection (Since she said her bladder felt small and she's been peeing outside her litter box every now and then) and gave us some antibiotics that I should start giving her twice a day until the medicine runs out.
I'm not super worried, since she has still been eating, drinking, etc, and hasn't had any real changes in behavior.