Unfortunely IBS is usually DX by ruling out other disease entities and it is a painful, draining, brain-gut disease. I too have the same lower left colon pain and was told that is where the stool basically is stuck. All my test, CT,ultrasound etc are normal.
Peppermint tea, fennel tea, heating pads, have been helpful as is mild exercise. You have to educate yourself on soluable vs insoluable fiber to find the right balance so you can move your bowels.
Best wishes
IBS is such a bogus diagnosis. It just makes me angry how so many docs hear a digestive complaint and grandly diagnose this mysterious-sounding "disease" and pass the problem on to the next doc to figure out what is really happening. (Sorry - end of rant.) :-)
All IBS means is that the docs can't figure out your case, and assumes they have run an exhaustive investigation to rule out any known cause of your symptoms. Have you seen a gastroenterologist? Any edoscopic/colonoscopy tests? CT scan? Ultrasound?