When my Crohn's was more active, I had the same problem and gave up running for several years. I would try heading out and after half a block I would have to turn around and go home to the toilet. Now with my Crohn's under control (with meds and live yogurt), I'm much better and back to running 3-5 mile runs! Here's hoping your colonoscopy goes well (it's uncomfortable, but not too bad) and that nothing serious turns up so you can start healing and finding solutions that work!