If you have taken the pup numerous times to the Vet & you are not satisfied with those results, seek another opinion from another Vet.
May I know what other tests the Vet has done besides checking it's blood & stools? I have a feeling your dog either has an Upper Respiratory Tract Infection or Influenza.
I would advise calling the breeder & asking about the other pups, to see if they are healthy. If it is a reputable breeder, they will let you know. They also would want to know if something is wrong. If another pup has same symptoms, perhaps another Vet was able to diagnose it.
Hope I helped. Thank you for your advice Goldenaddict. The vet carried out a Distemper test using the test kit. Results negative. Vet inspected the pup's breathing with a stetoscope. He said he could hear significant amount of fluid in the lungs. Pneumonia was the main suspect. Vet recommended X-Ray is symptons persisted for another day. Pup continued on antibiotics and supplements. Pup also put on nebulizer twice daily. Symptons immediately subsided the following day. Less mucus coming out from nose. Easier breathing. No more coughing. No more vomitting. No more retching or flam induced noises. Pup extrememly playful when brought home. Went to vet the following day and left pup for a whole day again. Nebulizer twice daily. Vet said that the fluids in the lungs have reduced. Will be taking the pup to the same vet today to continue its twice daily nebulizer treatment. Wish me luck guys