[DarinBongo]

You need to call your vet and find out exactly what they tested for in the stool. Most of the time they just do a routine check for internal parasites, and then take a guess. I just learned this lesson from my breeder, because Bongo was having some loose stools for a few days in a row. Not as bad as you're describing, but all the more reason you need to call your vet again. You need to ask your vet to check for Giardia or Coccidia, which are both microorganisms that could cause Acute or Chronic Diarrhea. These are not included in the routine stool sample and need a different course of antibiotics.

Here's an actual quote from my breeder from his email which will probably help you out:
"Back to the Vet issue, the parasites that they checked for was probably worms, as they can not see Giardia without doing an Elisa test, but none the less Metronidazole is used to treat Giardia as well, but Fenbendazole is better…which goes by the street name of Panacure which is manufactured by Intervet, the same manufacturer that produces the Proguard line of Vaccinations. Panacure is also a dewormer, the difference is that for worms you use it only 3 days, while for Giardia you use it for 5 days, and sometimes in conjunction with Metronidazole. On the Metronidazole, the dosage is 5 mg per 1 lb, so if he is 64 lbs, you should have given him approximately 320 mg, which means that you probably should have given him 1 and ½ of the 250 mg tablets."