Reminds me of when my mate's cat turned up after going on the missing list for about a week... he looked awful and smelled worse... he was tired and listless and looked like he'd been through the wars.
So my friend trundled him up to the vet, who examined said moggy, gave him an injection and presented my friend with a bill for £70.
"But what's wrong with him? What was the injection for? What should I do?"
"Oh that's simple. I've just given him a vitamin shot. Your cat's suffering from sexual exhaustion and just needs plenty of rest. He'll be fine in a day or two."
He was not a popular cat for some time afterwards!