Please don't let your vet give your baby all those shots at the same time again. That's way too much for his little system and can cause a disease called GME. GME can be deadly and when they do live through it, GME is not curable only treatable. Ask your vet to separate your babies vaccinations in the future. I would definitely take him back to the vet and make them do something. If he's still having diarrhea he needs to be on IV fluids as he will dehydrate quickly. He is in serious trouble now so I would not waste time getting him back in to a vet. If I were you I would be finding a new vet ASAP, one who knows allot more about small dogs as this vet should have known better then to give all these vaccinations all at the same time.
