You want TMI??? Allow me to introduce myself as your IBS guru.

I've had it for 10 years and help out with a support group in the Toronto area.
IBS is a diagnosis of exclusion, meaning there isn't anything organically wrong with your GI tract, such as cancer, colitis, Crohn's, etc. There is a whole brain-gut interaction and memory on a cellular level at play here that I won't bore you with.
A diagnosis of IBS is given when a patient presents with altered bowel habits for a period of 12 weeks (need not be consecutive) in the last 12 months, having a combination of at least two of the following: pain relieved by defecation, altered frequency, and/or altered form. Urgency, a feeling of incomplete bowel movements, passage of mucus, and/or bloating are also some of the fun things IBSers get to live with. IBS-D (diarreha) is classified as 3 more bowel movements per day, and IBS-C (constipation) is classified as less than 3 bowel movement per week. No, IBS-C is not rare. There are also the IBS-C/D for those who alternate, and lesser known but sometimes referred to IBS-G for those who suffer mainly from gas. And although it has been labelled as predominately women who suffer, many men do, too. It's just that women are more likely to seek treatment.
Symptoms that are not indicative of IBS are those that wake you at night (pain/diarreha), presence of blood, weight loss, or fever.
If you are taking a fibre supplement of any kind, it is imperative that you drink LOTS of water. Otherwise, think cement! If the fibre supplement is causing cramps or gas pain, try backing off the dose and gradually building up to the recommended daily dose over a few weeks. Some people do best starting with a dose as small as 1/8 teaspoon in a glass of water, and building up to the usual dose.
If you need any more info, just ask. I'll gore you with the details.
