my cat is really sick.. can some tell me what it MAYBE COULD be?

He got out about a week ago and was gone the whole day and night, until about 5am in the morning when I heard him meowing at the patio door.

Immediately from the moment he came inside, I noticed his meowing was different. not really hoarse but quieter, and just different.. I can't explain much more than that. And he kept hissing as he walked passed me.. I was concerned but I assumed(more like just hopped) he was just pissed me for not hearing and letting him in sooner. but he's kept it up ever since. he's always hissing and meowing every time we touch or go near him. his fur has been looking a bit unkept but other than that he's been eating everyday and drinking water. no other signs of illness until today.

About an hour we got home from the store and he was sitting in front of the patio door in his own urine and looking pretty unsteady, like ever so slightly swaying back and forth. I went over to him to let him and he nudged me a little and just walked off..

what could be wrong with him??? I know he needs a vet and I want to bring him to one so bad but I'm currently out of work trying to finish my externship not mention 13weeks pregnant, and my s.o lost his job and we have solely been surviving off of him doing uber and lyft driving which has been barely enough for us to scrape by. I just don't know what to do and I'm devastated