I wonder if he could have had some kind of accident ,got trapped, kicked and is bruised ..
I'm not sure if this is the problem, but my cat was hidding alot too, she wasn't moody though but every cat is different. She also didn't use the little hardly at all. But, she did hid alot(which was abnormal for her too) and she also didn't eat alot and I took her to the vets they took some urin from her and they said she ad a UTI. Maybe you could take him back to the vets and tell them that you'd appreciate it if they took a urin sample or something. I hope your kitty gets better.
I agree with Opus. Your cat is an older cat and any behavioral changes can be considered important and potentially life-threatening. He is not acting like his old self and being 14 he is definitely getting up in age. I would definitely take him back to the Vet tomorrow for a Urinalysis and bloodwork would be good too to check his kidney and liver functions as well. Good Luck...I hope he gets to feeling better!
well all I can say is I can't believe the Vet didn't do at the very least a urine sample...at this age and being a male I would highly suspect a UTI with or without crystals...and either can be very serious and very painful. Cats will typically go into hiding when they are in pain.
seeing tomorrow is Christmas day you aren't likely able to rush him back in for a urinalysis for a couple days, UNLESS he stops passing urine than its an EMERGENCY...bladders with crystals can block and burst.
feed him canned food, male cats need the extra moisture than can food provides and try everyway you can to get him to DRINK...water....
If its crystals plus a UTI than he will also need antibiotics very soon.
If it were my cat I wouldn't wait, I'm really upset with the Vet that didn't check this out for him.
Of course it could be a many other problems...this is just my guess of the most likely.
Did the Vet even do bloodwork?
You are the best judge of your cat not acting normally and like I said the hiding too are both indications of PAIN.