Whats going on with my cat?

PLEASE READ ALL & COMPREHEND IT TO THE FULLEST, SO YOU HAVE A GOOD UNDERSTANDING! i have a female cat, shell be 32 cat years in june. shes not pregnant because we got her reproductive system removed when she was younger. Every time i feed her, a hour later shes hungry again. im not feeding her little by little, i give her two handful, which over feels the bowl. She eats Purina Complete Formula. whats up with her? this has been going on for months. im getting annoyed a little, because it seems like every other week im buying her food. Also i doubt it if shes greedy because i used to only give her a half of cup food, then that's when i started giving her more because she was always hungry.