Vets don't know whats wrong with my cat... She won't eat?

For the past 3 months my 2 year old female cats condition has been deteriorating. She has lost a massive amount of weight, refuses to eat, still drinks but not much, has a fever, is dehydrated, and hardly has the energy to stand and walk around anymore. We have been to the vet's office numerous times and they have only given her antibiotics and fluids.We had her tested for AIDs and Lukemia, which turned up negative. A full blood screen showed nothing but an increase in white blood cells, which could mean infection, but they have no idea where. She is withering away and I am considering Euthanasia to spare her pain. But, I was wondering if anybody has any idea what is wrong with her that the vets might not have figured out before I took such drastic measures. Thanks.

GET HER TO ANOTHER VET AND HAVE HER CHECKED OUT IMMEDIATELY AND GET A SECOND OPINION BEFORE SHE DIES...........THIS IS NOT NORMAL..FOR ANY CAT........I CANNOT BELIEVE YOUR VET CAN NOT COME UP WITH ANYTHING. GO FOR ANOTHER VET IMMEDIATELY I HOPE ONE WILL FIND OUT JUST WHAT IS THE PROBLEM AND SAVE HER...............GOOD LUCK AND GOD BLESS YOUR PRECIOUS LITTLE KITTY........I SEND YOU GOOD THOUGHTS AND PRAYERS AND HOPE FOR A SPEEDY RECOVERY WITH A NEW VET

'The causes for a lack of appetite are many and varied. In some sensitive pets, even slight discomfort due to an injury, upset stomach or a change in home life will result in a complete refusal to eat, while other pets will only stop eating when seriously ill.
In other cases, particularly when there is no sign of an upset stomach, the cat鈥檚 refusal to eat is often the result of an illness or injury. Respiratory illnesses in particular are notorious for triggering inappetance.'
http://cats.suite101.com/article.cfm/why...

Have you had her screened for diabetes?

What about different foods? Kitten food has a high caloric content. You might also try a very high quality food. Innova cat and kitten has a crazy number of calories in it.

EDIT: What about her teeth? My cat had major dental disease at age 4. Almost all of her teeth were removed. I'm sure she was in terrible pain - maybe that's the problem here.

have the vets done x-rays of her throat?

This is definitely time to see a different vet. Now.

have you done any kidney tests? some cats are prone to major kidney failure. and also talk to your vet about FIP (feline infectios peritonitis) . these things are often treatable if only enough resources are put in to diagnosing the right condition . there are a few major organs that should be checked with an ultrasound just to check for stones or a inflamation due to a viral infection. if you have the patience and the funds , try taking your cat to your local emergency vet hospital or a university hospital where they have alot more equipment to diagnose conditions for animals.