we bought a puppy and for...

Question
we bought a puppy and for the last 3days he has had diarrea and today he threw up.what do you think it could be?

Answer
If he is not up to date on his vaccines (puppies need vaccines every 3 weeks from age 6-8 weeks until they are 4 months old), I would be very concerned about parvovirus which is a life-threatening intestinal virus.  You really need to get him to the vet.  It could be a less serious viral infection or intestinal parasites, but he needs to be checked by a veterinarian to determine exactly what is wrong with him and get the proper medication.