C-Diff Vs. Ulcerative Colitis

I was diagnosed with C-Diff in 2002 which apparently led to UC. I was scoped 1 yr later and my colon was free and clear of any ulcers. Last August I cam e down which what myself and the docs that was food poisoning. i checked myself into the hospital after 2 days of severe cramping and diarrhea. Due to my history, the docs put my on Vancomycin and treated the illness as if it was c-dd even though the stool specimen came back negative for c-diff. my stomach has not been the same since. i took predisone right before i got married in january and that healed me right up. i have been having some issues over the past 6 weeks and i am currently on prednisone, vancomycin and lialda. Any thoughts on what's going on?