Cat has persistent diarrhea-Help!

Our cat has had diarrhea for over two weeks. When it first developed, I took her to the vet, submitted a fecal sample that came back normal and was sent home with an Rx of metronidazole, 1 ml/2 x day for a week. Getting her to take the med was very hard (it's bitter, she'd clamp her mouth shut, and some of it wouldn't make it in). Nonetheless, we did it.

Since then, her stool has improved some, but is still very soft/unformed, and she goes several times a day. We feed her 3+/day wet kittenfood and she has free access to dry food (she doesn't like dry very much) and she is still struggling to maintain her weight.

Factors to consider: She is a queen with 7-week old kittens that are weaning, but still nursing some. The vet checked for mastitis, didn't detect it, but she had a low grade fever when we took her in two weeks ago.

I have called the vet twice for help. They are slammed and I haven't heard back. Considering taking her elsewhere. But I would love to get some feedback before I fork over more money to someone else for the same (non) result.