Spoke too soon?

Callay was feeling a lot better. She was eating, she looked to be putting on weight, she was acting almost like herself again. So much so that I almost decided against taking her to the vet's for another checkup, but I took her to Banfield, since we have something akin to doggy insurance that makes checkups free. Well, she was running a fever, and didn't really want to eat that day, or over the weekend, and even until today. I've kept her going with gentle force-feeding (shove wet food in the side of her mouth until she swallows it) but this is not a good thing.

She's at NCSU yet again, this time for an ultrasound to see the current condition of her internal organs, if something has been damaged by all these antibiotics, if she has some lesion, or if just like all of the other tests, it shows "nothing conclusive"

This is so very difficult. If we just had an answer from this battery of tests. . . But for her to go downhill after 2 weeks of feeling really good. For her to spike a fever while still on potent antibiotics. If we just knew what the hell was causing it, we could decide. . . something. She is still acting like she feels fine. She just has a fever and doesn't want to eat. But say the words Walkie, Cookie, ride in the car, and she's bouncing all over the place. Take her for a walk and she wants to jog the whole way. Do we let her stay where she feels good enough to do all that but doesn't want to eat? When do we stop and just let whatever's going to happen happen? After what we have put into this, how do we stop now? How do we just give up on the best veterinary hospital in the state and just see what happens? I really don't believe they're pushing tests on us that they don't feel are necessary. They do seem to be acutely aware of the fact that their reputation is being tarnished somewhat by the fact that they're doing all these tests and still don't have an answer for me or for themselves. I keep asking how this test or this test will change her treatment. They always have sound answers.

I'm frustrated, sad, and worried that I'm making the wrong decisions for her care. Every test seems like it's a good idea and it will answer something or rule something out. And then it doesn't.

So what do I do?