He's about 13 yrs old and has been coughing and gagging. Usually drinks lots of water but isn't doing that either. Just wants to sleep all the time.

At 13 your dog is considered geriatric, these are problems best addressed by your vet.
It could range from kennel cough to cardiac problems. A vet is your best option at this point.

At 13 your dog is considered geriatric, these are problems best addressed by your vet.
It could range from kennel cough to cardiac problems. A vet is your best option at this point.
Thank you, I am on my way to the vet. He now won't put any pressure on his right front paw. Still won't eat or drink since yesterday. He's 14 yrs old and I'm afraid of the outcome.

Good luck I wish you both the best.