I dealt with IBS several years ago which was the start of a downward spiral with my health. The underlying cause ended up being candida and parasites. It is a sign that your system in imbalanced. You need to make sure and be taking good bacteria (probiotics) and do some sort of candida and parasite cleanse. Let me know if you want more details.
There are a few things I have tried and 2 of them have worked. The first one I did was I read a book called Eating For IBS by Heather Van Vorous (http://www.helpforibs.com). The book along with the website and the things she recommends to help all really worked for me. She has an insight into this horrible affliction that I found no one else had. I recommend the book and the website 100%. She only uses natural products and instructs you how to eat where you don't take in the foods that trigger IBS.
Also, I am currently in the 11th week of the Lifeforce Candida cleanse and the only stomach problems I have had are when I cheated on the program. Since week 2 I have had no IBS flare ups at all but when I cheated.
There is really help out there and I have tried many, many things to get the help and both of these things I wholeheartedly recommend.