Oh Stomach flu, what a glorious time......this past January there was an evil bug that went around town that i of course contacted. I'd been diagnosed with IBS for about 2 years at this point but it was all C and no D. The D came on like a darn hurricane. 1 week, 2weeks, 3 weeks...= scarred out of my mind! I was going almost 7 times a day and lost about 6 pounds in that time frame. Finally I went to my doc and said, I think there's something wrong here. He said IBS can make one have a hell of a time getting over a stomach bug. He put me on Xilflaxin (sp?) which is usually prescribed for traveler's D. Its an antibiotic that somehow stays in your stomach and is not absorbed through the lining so it can target the bad bug that won't leave. It took about 2 weeks after I started on it (2 pills a day for 5 days I think) before I felt "normal" again. I had a cup of coffee after 3 months and felt like I could climb everest, it was awesome. Anyhow, point being, if you can't shake it, and feel ok about antibiotics, then I recommend that one. Just be sure to get on a pro-biotic regime to restore your good gut flora after its all groovy.
Hope that helps.