Inflammatory Bowel Disease can be tricky to diagnose, and so can Irritable Bowel Syndrome. They have lots of similarities. Generally speaking, all of the diagnostic tests (including colonoscopy, small bowel series, CT scan, stool tests, blood work) will be negative if you have IBS, and at least one, but probably more, of those will be positive if you have IBD. Sometimes you can have some positive tests - I myself had an abnormal small bowel series and abnormal stool studies - but they still are hesitant to diagnose you if you are not a "typical" case. It's weird, but understandable - our guts are really difficult to understand and docs just can't know absolutely everything about them. I'm still waiting for a diagnosis. Have been for a year.
My guts got a bit better there for a while; I started going 2-4x/day instead of 6-10 and that was great. It occurred gradually and then they gradually started getting worse again. Now they are back to "baseline" (6-10). My advice to you is to keep a symptoms diary and a food diary that you can bring to your GI so he can see how your symptoms are on a day-to-day basis.
Your colonoscopy should tell a lot. Good luck!