I, too, have Irritable Bowel Syndrome (ever notice that when you mention the word "bowel", people back right off?), I've had it for as long as I can remember, even as a toddler. Whenever I am nervous about the slightest thing, my stomach acts up. So that is often.
I finally had enough of it when I was about 22. The doctor thought it was reproductive problems but it wasn't, so then I got the diagnosis of IBS. I still had a laparoscopy to make sure anyway. It was quite painless, I was surprised.
Right now, IBS is driving me crazy, I can't go out for very long. I have tried medications, it is like eating lollies. I am going to ask the doctor about allergy testing to see if I am allergic to any foods. I will insist (as best I can) this time, I sort of got brushed off last time.
Luck with the colonoscopy, flea, let us know how you are?