Last night I found my 1.5 yr old cat under the bed hardly moving. I pulled him out and he got up and walked away, obviously in pain. It's been almost 24 hours now, and I haven't seen him urinate or defecate. He just stands in the litterbox a while and then gets out. He keeps going under the bed, and when I pick him up he's like a limp rag. I was afraid he'd gotten hurt, but he's an inside cat and he can walk ok. Usually he's extremely frisky and jumps around alot. I thought he might be constipated b/c he has had a hairball problem since the weather has warmed up and he's losing his winter coat. I gave him some hairball medicine but nothing yet. He seems to have sensitivity around his privates, he's neutered but there seems to be some irritation, like a piece hanging out. His anus seems fine. I haven't seen him eat more than a bite, but he seems very aware, not too sleepy or lethargic. He also seems to be breathing harder and his mouth hangs open a bit. He's due for his shots but it's not overdue. Is it constipation b/c of hairballs or urinary tract infection or something else? He also puked up a bit of liquid this morning and a hairball last night. He doesn't seem to be getting worse, but not better either. He lays on his side and keeps his tail and rump lifted when he's in sitting position. He doesn't react to things that he usually reacts to, like messing with his tail or paws. I'm planning on bringing him to the vet tomorrow, but I'd like some idea of what it might be. Other factors: we have another cat and they tussle alot, but overall Magellan's happier now than before we got Katie. Also, I noticed the window seat had fallen down and I thought maybe he hurt himself on that, but it seems internal.