It might be good to call your doctor. It sounds like you realize you're in another flare so just sticking with the meds you're on now may not get you out of it. And as you suggest, some form of rectal meds may help. Try to read some of Quincy's posts. She is very knowledgeable about them.
You also might want to ask your doctor to check stool samples, since this started after being on antibiotics. You might have something like C diff (I say this knowing that I probably need to do the same thing, after being on amoxicillin in June).
Potato... Female, 58, dx mild left sided ulcerative colitis 11/07
asacol 3 3x a day
am & pm
culturelle, benefiber wafers
children's vitamin, Vitamin E 400 mg
omeprazole 2x a day
oxazepam when needed, lomotil or ImodiumAD (but not in the same day)