Our dog hasn't been himself lately. He usually is very excited when getting out of his cage to go outside to the point it is hard to put his collar on. Now he just stands there. He does eat and drink but now as much food as usual. We have tried a over the counter roundworm de-wormer liquid. So far we have not seen any in his fecal. He might have lost some weight. He doesn't whine or act like he's in pain. He is 9 years old but has always acted like a puppy. He is a Jack Russell Terrier/Lab/Australian Shepard mix.

Changes of this nature are best addressed by his vet it could be many things, and at the age of 9 he has entered into the senior years where things like diabetes, kidney issues and arthritis could be a problem.
I would suggest having him checked thoroughly by a vet, including blood work to check for age related changes.