I'm not sure. You can get fungus (ringworm) from cats, in which case it's very hard to get rid of. Sometimes it requires oral antifungal antibiotics. I'm also not sure which test on the cats came back negative--fungal cultures, the definitive test, takes a month before it's considered negative. If this is a fungus, cortisone creams and shots are likely to make you worse. I think you need to see a dermatologist, who can examine you and perform the needed tests to tell you for sure what you have and to clear you up.
Take care.
Dr. Rockoff