Desperate - Ideas for my very poorly cat - any vets?

[noarguments]

Very poorly 9 month old cat - had high temperature and feeling rubbish for 10 days or so. Multiple vet visits. Normal Antibiotics and Metacam given with only short term improvement. In at vets all day yesterday for blood tests - negative for feline versions of HIV and leukaemia. High platelet count - vet wondered about a different sort of infection and gave a different antibiotic injection plus steroid, back to vets on Monday but still looking awful today. Extremely lethargic, and weak. Eating the odd mouthful here and there, but nothing more.
Anyone got any ideas of what this could be?
And also what could I tempt her with food wise? She really needs to eat something.

Sorry for radio silence.
We've now had three whole days of fluids at the vets, really struggling to get food down her still. Temperature more or less normal now, but has lost her appetite completely, and she is just so weak - we can't go on like this for ever. Just discovered syringing food (the convalescent stuff the vet gave me) on to her tail or paw, and she'll lick a bit off.
Emotionally draining - we just want her better.

It is so hard when they won't eat. Have they tried any appetite stimulant medication yet? My cat had two different ones Mirtazapine which is given daily and unfortunately I can't think of the other one which was every three days but it did help.
I hope she starts eating better soon.

Very sad to report that we had to have our little pussycat put to sleep today. It was a very hard decision to have to make, and I'm too much of a wreck to explain it just now, but I do think it was the kindest thing to do. Thank you for all your suggestions and handholding.

I'm very sorry.

Oh no I was hoping she'd pull through. So sorry for your loss.

I'm so very sorry

I am so sorry. Poor you. Its so hard, isn't it.

Very sorry to hear this, poor you and poor pusscat

So very sorry to hear your heartbreaking news. I have been following your post and keeping my fingers and toes crossed for you. I didn't like to post as it sounded so similar to how I lost one of my lovely cats about 3 years ago. He had pancreatitus and I remember you posting about this being a possibility for your baby. Awful, awful illness. I so know what you are going through.

I'm so sorry to hear this news. 9 months is still just a kitten.

That's sad, thinking of you. Xx

So sorry to hear about your little kitty.

I am so sorry to read this. I lost a cat v young to an unexplained infection. It was heartbreaking. Thinking of you.

noarguments, I'm so sorry.