I am so frustrated....Our puppy has dirrahea really back...she has had it sence we got her from the breeder...treated her for cocidea, gardia, whip worm, changed her food 4 times...had her on metrodizanole...pepto bismol...did 3 stool samples and still the vet cannot figure it our....anyone have any idea's....
How old is the puppy? How long have you had her? Changing a puppies food so many times may be a contributing factor. Some dogs have sensitive stomachs and switching foods like that can create problems. If treating her for worms has not helped, and putting her on metronidazole has not worked, you may want to have a fecal digestion panel done on her to check for pancreatic insufficiencies. I wouldn't suspect that in a puppy but it would be the next step. It can be done one of two ways, either through a stool sample or a blood test. What food is she on now? My mom had the same issues with her GSD when she was a pup. Putting her on Pro Plan's salmon and rice sensitive skin and stomach formula worked wonders for her. You may also want to consider mixing in some pumpkin or yogurt into her food at each meal and see if that helps.
If you have treated her for all the things you have said, have you given this pup any type of probiotic to replenish the good bacteria in her system? Wormers and medications strip the system of good and bad bacteria, and not replenishing can lead to continued digestive upset/diarrea, etc. I suggest you purchase a good probiotic to give to her as well as supplement called Dyne to help combat her dehydration and lack of nutrient intake.
I also second the suggestion to immediatly stop the consant food changes. Stick with one quality food (something grain and preservative free) and give it some time.