it could be his teeth, keep him inside to observe him. If he is stress, get his companion w/ him as well indoor.
if he's eating, but not eating much, it can easily be a molar causing the above symptoms.
I can't afford another dental not at the rates my vets charge!
I can't get insurance now as they have known problems so it's too late, I'll monitor him over the week end and if there's mo change by Monday I'll take him.