Another round of doxycycline. And the vet insisted we take him to see the specialist internal medicine vet guy up in Langhorne asap. The regular vets just don't have a clue as to what is wrong with the Little Dude. It might be the effects of a long-ago left-untreated Lyme situation, or it could be autoimmune (He could have lupus! I'm not even joking - lupus!), or something kidney-related.
Poor little guy!