How long has this been going on for???? Is she spayed? When did it first start? (after Vaccines? her age when it started...her age now?? Is she on heartworm medication? Do you use flea and tick treatments on her? It can be related to a LOT of different possible things...Her food...even if you are feeding a so-called PRIME (expensive) brand...it may NOT AGREE with YOUR dog...they are all individuals! Have you ever tried a raw diet? Or a home made diet? You can run a google search on B.A.R.F to read up on raw diets and then one on Homemade Dog Food or Dog Diets to learn more about that. http://www.api4animals.org/facts?p=359&more=1 This site has a lot of very good information to start learning more about canine nutrition...and about commercial feeds...pros and cons. To try and firm them up add about a tablespoon of PLAIN canned Pumpkin to her meals...contrary to what one might think...this does work to help firm up stools. Do you have a cat (cat box?) could she be getting into "Kitty Rocha?" Even the nicest doggie will sometimes indulge in the forbidden cat poo snack, gross as we find the idea to be. Internal parasites can also cause this so I would suggest that if you have not already done it...snag a sample and take THAT to your Vet so they can run it through the lab...better safe than sorry. The only worm you can generally see in your dog's stool or on their back end is a Tape Worm, caused by the dog ingesting a pregnant flea. (looks like bits of white rice that move.)