Reoccuring Radiating Discomfort

Occasionally, for periods of one-two months I feel like I am constipated.  It almost feels as if the lower left quadrant of my intestines are blocked up.  I get gas, bloated, and I do not have the normal urge to go to the bathroom or bear down.  When things do release from this point in my intestines I can feel it moving past this point (internally) and it usually comes with intense pain, gassy stool and watery stool (not necessarily diarrhea).  I have not had this in over two years.  My stress level is fairly low compared to the past two years.  My diet is much better, and fiber intake has been adequate.  I have tried taking in more fluids, to no avail.  

The strange thing is, I can now tell when a bout of this painful experience is coming on because it will radiate to the back of my left thing, and occasionally into the arch of my left foot to the point where I actually have a minor limp in my walk.  

I have avoided dairy, caffeine, and artifical colors and flavors.  I have been to a specialist.  I have no diagnosis of diverticulitis.  They could not find anything else wrong when they did a colonoscopy.  

What is this and what can I do to relieve this, either with my diet or medication.