Until your vet can do a thorough physical exam on him and determine what is making him so painful, there aren't any suggestions. There is nothing over the counter for pain meds. Has there been any recent trauma or any event that the pain seemed to start after? Does he eat things he is not supposed to like getting the trash, toys, etc?
Dogs hide their pain very well.......If your dog has been yelping for 2 days, then he is in extreme pain and must be seen by his Vet ASAP.......Please, do not try any OTC pain products....Most are poisonous to dogs!
Your Vet will have a pain management protocol after a diagnoses...Good luck, let us know what you find out.....Please make the call......Karla
Agree! He needs an exam, and soon, to determine what is causing his pain. It may be something internal or an injury.
Please get him checked out