9 year old pointer keeps losing weight still eats and drinks had blood checked and stool came back fine what else could it be hel[p

What type of blood work was done? What did the vet check for? How much weight has the dog lost? What is the vet suggesting?

Maybe it's the food you are giving your dog? You should switch to ones with more fat in them and give it to him/her three times a day for a week if still no progress see your vet. If there is progress then after your dog is normally plump switch her back to his/her normal food again.