Cat very sick with Intestinal Illness

[Ladybugg097]

My 7 year old cat has been having off and on diarrhea for about two months, as well as losing weight. She has always had an allergy to fish, but for years had been fine on the Science Diet Naturals chicken food. We wormed her and tried changing her food around, nothing worked. During this time she was also ravenously hungry, stopped using her litterbox, and generally wasn't herself. Last week she totally stopped eating, and was very lethargic and dehydrated. We took her to the vet, they did bloodwork, and the only thing abnormal was a low WBC count. No signs of any other disease. The vet did not know what the WBC count meant. They gave her fluids and told us the next step would be an ultrasound. I cannot afford an ultrasound, so that option is out. I brought her home, and have been doing research on IBS and other bowel diseases. I have changed her food to a wet food with only venison and peas in it, and started her on slippery elm bark and an acidophilis supplement. Anyone else experience something like this with their cat? Any suggestions, at this point it is a last ditch effort or I am going to have to put her down.