It should be fine to take the Pepto and the Pred near the same time. Do you know for sure that you don't have some sort of flu bug? Maybe it's not the UC causing the problems right now, maybe you have a stomach bug. My daughter had it last week and so did my friend's daughter. There were 4 kids absent from my daughter's class with it too. I'm just suggesting it because it sounds like these new symptoms came on suddenly. I get occasional nausea from UC but never vomiting from it.
I hate to say it but it sounds like this 10 mg of Prednisone is really just toying with you. I've never heard of anyone starting on such a low dose. To nip a flare in the bud, it's best to just go for it and do the 40 mgs. I would also consider the cortenemas. I started them over a week ago and after the first day or two, I felt 100% better. I feel like doing the 10 mgs. is just prolonging things for you.
Female, Age 38
Diagnosed w/c.diff 7/02 when pregnant w/1st and only child during 2nd trimester(wasn't on antibiotics)
C.diff flare within weeks of delivering baby 1/03, Diagnosed with UC 2/03
Acidophillus, Sacchromyces Boulardii, Oil of Oregano