You need a vet immediately. That could be something like a serious injury, a bite, or an infection that can move into the blood stream and kill your pup very quickly. It's not something you watch and wait on or even call in case it can be resolved over the phone because it might be okay, it's not. I hope your baby is feeling better soon.
5 month old puppy very lethargic sick for 7 days had blood work done everything looks good except white cell count high doesn't want to walk not eating that great and his paws are swollen now