What Causes Frequent Diarrhea And Abdominal Pain?

I have diarrhea ever month about the same time. My stomach hurts like someone is taken a blade inside my stomach. I sit on the toilet at least 3 times for 30 min each time. At first it was a reg bowel then its diarrhea so bad it s liquid. It happen every three months as well But lately it s been ever month. On my medical it said I have IBS. Please help me understand it affect my job because I am in the bathroom 30 min at a time. Thank you