What Causes Sudden Change In Bleeding Pattern?

Hi, i'm 34 years of age with 4 children. my periods have always been very heavy, but last month they arrived two weeks late and was very very little flow and lasted only two days. This month I was due on the 6th, and I am still waiting. today i started experiencing a dragging sensation in my lower abdomen and feel almost "bloated" in the area? Urine and Stools are normal, health is ok so i'm kinda starting to worry!!