I agree with Jan that a vet visit would be the first step. It could be something simple like thyroid out of whack (which isn't a stretch of an idea) or it could be something like an infection from the hip replacement.
I would want a full thyroid panel done. Not sure where they would send the blood for that there. Here it is typically Michigan State or Dr. Dodds/Hemopet.
I would also want a CBC/super chem done - to get an idea of white cell counts in particular and then to find out everything else.
UTIs can cause pain so toss in a urinalysis and not sure what the status of worms/parasites are over there so fecal too.
I am not sure how long you've been injured (MY GOSH!) and how it coincides with his behavior, but do know that when I have been feeling unwell, I do have a dog who is a therapy dog who does a complete change and takes over. I think I am communicating I am capable, but she senses otherwise. Can't get anything past her!!!
I would still start with the vet stuff. Best to you!