Why does my puppy still have diarrhea?

Ok, this is a long story so I'm going to try to some it up. I have a 6 month old small breed puppy that was spayed three weeks ago. The day after her surgery she had diarrhea about 6 times, so we took her back to the vet. The vet thought she might be sensitive to her pain medicine so took her off of it and put her on an antibiotic/antidiarrheal and a diet of boiled chicken and rice for 3 days. A week after the spay I came home from work and the puppy had diarrhea and vomited all over and continued to do so - both were dark brown in color. I rushed her back to the vet where they told me that she was probably allergic to the antibiotic and told me to stop giving it to her, but gave her two medicines; one for diarrhea and one for an upset stomach and to put her back on the bland diet for at least a week. The next day we were back at the vet as her incision from the spay was oozing, there was no infection but they put her back on a different antibiotic. The day after that she was not eating, started vomiting and was lethargic the entire day (this was the first time she exhibited symptoms other than diarrhea/vomiting) the vet told us to stop the new antibiotic but keep her on the two medicines for her tummy. She seemed to be doing better so after a week of no vomiting we started weaning her off the bland food by mixing her kibble in, and then increasing the kibble and decreasing the rice until she was on just kibble. The first day she was off the bland diet she pooped ALOT (6-8 good size poops) but we thought maybe she was just backed up from all the rice. The next day she started having loose stools but we figured she needed time to adjust to being back on regular food. We haven't given her anything other than kibble, no treats or rawhide or anything. For the next two days she had diarrhea on and off, and today it has been all diarrhea thats a nasty yellow color. I tried calling the vet tonight but they closed early, and since she is acting ok I didn't feel the need to call the emergency clinic, so I will call our regular vet in the morning. She is still acting fine, even a little more rambunctious than usual, and until today had a pretty healthy appetite. I am worried about her, and concerned that with the medicines (which she finished a week ago) and the bland diet may help but they are only treating the symptoms, not the actual problem. I do not know if it was related to the surgery or not, only that it started right afterward. Has anyone else experienced this with their dog, or do you have any ideas or questions that I can talk to the vet about? Thanks!!!!