I was suspecting you may have IBS due to your symptoms, but as the colonoscopy showed the diverticulitis is the reason for them. Mild cramps, bloating, constipation are symptoms that one with diverticulosis can have and are similar to symptoms of IBS.
The most common sign is tenderness around the left side of the lower abdomen, like you have experienced and also, it can be due to constipation in IBS patient.
I hope your results will be ok.
Please, share them as soon as you get them!
All best to you!
Marija