my puppy is in pain dont know why/ what to do

Question
a week ago, I took my puppy to the vet for physical/diharea treatment, so the doctor their did a fecal test and decided that there some type of bacteria that causes the diharea/blood and gave me couple of antibiotics that I should give my puppy for couple weeks before seeing him again.
so I did for the first week but then yesterday the do started screeming whenever he tried to sleep or rest vocalize in a painful manner every time he puts his head to rest he screems and no position is better for him they all seem to hert him.

Answer
Vets can never be completely sure what is wrong with a dog and what treatment will work.  This sounds like a case where you need to get back to the vet at once.  To get him through the night you could give him some aspirin, buffered is best and you may need baby aspirin to get the dose right.  It is 5 mg per pound of dog.  a 20 pound puppy would need 100mg, less than a third of a standard tablet.  Aspirin, not Tylenol or Advil.