Most people who have diverticulosis don't have any symptoms, but some have mild cramps, constipation or bloating. Diverticulitis causes more severe symptoms, including any of the following, but particularly the first two:
Steady abdominal pain
Tenderness to pressure in the lower abdomen
Change in bowel habits (constipation or diarrhea)
Sharper pain with breathing or jarring movements such as walking.