Whats wrong with my cat?

he was gone for 3 nights after a girl cat & he didnt have no food either,he doesnt know how to hunt,cuz hes indoor kitty.so he came back, & i fed him he seemed ok.but today hes very sore on his back feet & theyre swollen and he doesnt want them touched, & has a high fever,& his back hips jitters. whats wrong?