What Causes Lower Abdominal Pain And Back Pain During Menstruation With Heavy Periods?

Iam 38 year old woman with 2 children aged 5 and10. I have twinges of pain in the lower abdomen and sometimes it is a dull continous pain especially during ovulation. A couple of days before menstruation I get severe stomach pain as well as pain radiating from the lower back to the stomach followed by heavy menstrual flow.