Thank you for the additional information.
I am very sorry to hear that Jack Jack has not been acting himself. This is concerning since he normally plays fetch and has much more energy. His symptoms are somewhat vague therefore giving you an exact diagnosis is going to be difficult. Whimpering is most commonly due to pain or discomfort in his body. This can also cause a decrease in the energy levels. Other common causes of lethargy would be a fever from an infection, an organ disorder such as kidney or liver disease, an upset stomach
(though most dogs will not eat also), and a cell count disorder such as low platelets or red blood cells.
At this point, the best way to get an exact diagnosis would be to have your vet examine him. If he continues acting lethargic and whimpering I do think that a veterinary visit would be worth while.
The most common cause of discomfort in a smaller breed dog would be back or neck pain. This can be due to multiple reasons, here are some of the possibilities:
- IVDD - intervertebral disc disease - basically a bulging disc in the spine that causes some pressure on the spinal cord, back muscles
. This can be mild enough to cause some pain or unfortunately more severe to where the disc material pushes on the spinal cord enough to cause paralysis
to the back legs
- Muscle strain/sprain or soft tissue injury - This is the same thing that happens commonly in people. The muscles tighten up and can cause quite a bit of discomfort.
At this point, resting him is the best way to make sure that he does not get worse. If you would like to give something for the discomfort at home, you can give him some aspirin tonight. His dose would be 5 mg per pound every 12 hours. This should help with some of the pain. Aspirin is usually very safe though some dogs will develop an upset stomach therefore I would recommend stopping the aspirin if you see any vomiting or diarrhea.
Overall, if the aspirin does not help I would recommend having your vet examine Jack Jack to get a more exact diagnosis.
Hope this helps to answer your question - if not or if you have any more questions please feel free to reply by clicking on the "reply to" button. Thank you for your question.