If your symptoms continue to get worse, I'd get down to an urgent care clinic, or find another doc who is willing to do order a stool culture. I had a very persistent c diff infection that lasted two rounds of flagyl in increasing dosages, and then two and a half rounds on vanco. People that get c diff infections are also prone to relapse, and within 90 days I was back on the vanco. Used an increased dosage though, and 1 round got rid of the c diff. Been clear for over almost three years now.
One thing I noticed is that c diff and UC diarhea look and smell differently. Not to get to technical, but the c diff d was definitely smellier and had an oily sheen to it. Plus it was way bloodier and the sense of urgency was beyond anything I've experienced with just my UC flare. More stomach noises as well.
I sure hope that you've kicked the c diff and are just experiencing a flare now. The c diff made me feel so much worse than just UC, and UC is no picnic. Good luck, and go find a doctor who cares. You can't get better if your doc doesn't think you are ill.
36 y.o. male
Diagnosed w/ moderate UC in May '06
Asacol, Florastor, VSL#3, Wellbutrin XL, Prozac, multi-vitamin, Allegra, Lialda, Colocort enema, Prednisone (trying to taper down)