My cat left for 2 weeks, came back and now wont walk.. or move.. but eats fine.. whats wrong ? :(?

okay so my cat went missing for two weeks.. and then when he came back he was screatching and crying and wouldnt pur or even ignolige when you pet him. he just sat there .. breathing and all but he felt dead. he wouldnt use his hinde legs so we made him a bed carried him over to it. and hes now been inside for like 5 days. and those days he was peing inside and pooped. not in a little box but just all over himself. hes eating fine, appitite is usual. but.. his hind legs.. mostly his left one, he wont use it much . hes better now, hes purring and cleaning and he stretched both hinde legs out, but will hardly use them.. soo in other words.. he wont eat unless we carry him to the food, now were putting him on the deck to go to the bathroom. and he pees and poos outside, but not until after like 4 hours of sitting in the cold. iv tried moving his legs and if i get to touchy he starts getting agrivated. his left legs is still bad. and if carrying him we move it wrong he screatches and hisses and bites.. like.. it has a bunch where his knee would be.. but if it was broken he wouldnt be able to move it right ?.. so what could be wrong with him ?.. my dad batthed him when he first peed all over himself, and was ppulling on his legs and everything and he was fine. also when we put him near his food dish in the kicthen it takes him a couple mins to eat, because he looks scareed.. hes really skitish, and just. we cant take him to the vet because we may not have enough money to fix him.. we want to see if he wil get better.. so far he had, now hes cheerfull and nice until we try to lift him, like hes kinda moviing around on his own but not much and its been about a week since he came home. what could be wrong.. could it behis pelvic bone maybe ? .. something we couldnt detect ?