My cat has lost her entire appetite and is losing weight dramatically. Her blood results are fine though.?

I wrot about two weeks to get some advise as to how I should approach this and am very thankful for all the responses I recieved. I have tried everything, from opening up a fresh can of tuna to buying her kitty milk to buying her wet food but she just will not eat. Blood results show no problems with her liver, pancreas, she's not diabetic, her red and white blood cells are okay and no signs of thyrorid which makes this all the more puzzling and frustrating. Tomorrow she is going in for a sonogram. Dr. thinks it might be intestine-related or a tumor. She has developed three rather large hard lumps on her body, including in her belly area. She will drink water, however. I took her in to the vet last week and they gave her IV fluids and a shot of cortisone which stimulated her appetite for 9 full days and then she reverted to not eating again. Help! I am left wondering what about the cortisone shot gave her the umph to open up her appetite. To me, clearly, a cortisone shot helps the problem she is having, but what can that problem be? Could it be cancer? I have been reading alot about IBD (Inflammatory Bowel Disease) and it seems right, however, while she has excessive vomitting, she doesn't have diarreahea. This is so baffling. Any one have any tips to what it might be and sites I can go into that will give me some kind of answers. This is my way of doing my own independent research, aside from what the vet is doing. Thanks in advance!