You know, I really do think that even one dosage on antibiotic can really wreak havoc with the gut. It's the first question a naturopathic doc will ask when you speak with them: "have you taken any antibiotics recently?" I guess it would stand to reason that if you were doing okay before the antibiotics and there has been no other big change in your life (not counting stress because that's a daily thing!), I would have to assume that it at least contributed to your flare up.
For me, as someone who suffers with primarily C, taking OTC fiber supplements is a big no-no. I had been taking them for years and years: Metamucil, Citrucel, Fiber-Sure, etc. By the time I landed in the GI's office this last time, I had myself a nice little colon impaction! The doc told me that when you are constipated, adding more harsh insoluble fiber into the system will only make it worse. Because this type of fiber absorbs so much liquid from the colon, it can actually add to the C condition. And when you are FOS

, the colon can't move all it's contents on it's own. I don't take supplements anymore. I get my combination of soluble and insoluble fiber from food.
BTW: I actually had a great day today and thought about this thread! It's the first nearly pain free day in, well, I can't remember how long!