Still not healthy!

Emmy has been sick... since February... and I can't figure out what's wrong.
I think she attempted hibernation in Feb. She seemed to develop some sniffles, appetite dropped, she was on 2 different antibiotics for a month for a supposed URI.
For about two weeks she seemed improved, her appetite dropped again, and her nose is moist.
No green poop, activity is great. Even a weight gain.
Her appetite fluctuated for a while, and some nights the nose would be worse than others.
So I thought it could be pollen, the liners... etc. I called the vet, he said just keep an eye on her for now. I did for a few weeks, and then she started losing weight (activity is still great, still drinking water, poop still brown). JUST the appetite and a moist nose.
I took her in, doc floated a fecal sample, didn't find anything but thought it might be parasites anyway and gave me an antibiotic for her stomach to kill any potential parasites and he thought it would spark her appetite a little. Her appetite got minimally better, she hasn't lost anymore weight, but she's the skinniest she's ever been. Not malnurished, and her sides aren't sunken in, but still skinny.
So I have an appointment tomorrow, and I'm baffled.

What should we do to diagnose her? I really don't want to sedate her, and he said if things aren't improved he'll do bloodwork to see if that shows us anything. I was thinking an xray could be good. I want to ensure her liver is ok. I've been syringe feeding her to cause i'm worried about FLD.
Any advice would be awesome, thanks.

**ETA: She eats only the smaller kibble, and slurps the food out of the syringe, so I'm wondering if she just can eat the big hard kibble? Worst case scenario I'm afraid there's a tumor or something on the roof of her mouth. I've tried looking but can't get a good glimpse. :-/ I really hope that's not it though. I'm hopefully being irrational. **