Dog Sudden Behaviour change

Question
Hi,

I have a chihuahua & lasa-apso mix dog, hes 8 almost 9 years old and the other day he started to act kinda off. Usually i get home and he wants to play tug of war, or crawl on me. When i came home the other day he didnt even come to me, he wont play at all, and he only wants to go outside. When hes outside he doesnt want to go back in. I know he doesnt have to use the bathroom since i watch him go and theres nothing out of the ordinary. I have taken him to the vet and he thinks the dog might have hurt himself so he prescribed some pain meds. This was yesterday, but even now he sits across the couch and stares at me. I cant get him to do anything that he was doing before. I thought maybe something in the house scared him or at least spooked him but nothing at all has changed. Sometimes he will just sit with my g/f and shake his whole body like hes cold, but hes not cold. Any advise would be very helpfull, at this point im very concerned about him and dont know what to do.

thanks for any help you can give.

Answer
The first step is to take your dog to a DIFFERENT vet., Have a complete physical done. Any time you have such a drastic behavior change you look first to the health of your pet. Saying he MIGHT have been injured won't work. You need to know for sure :)
blessings,
Cindi