What Causes Pain In Lower Abdomen With Heavy Bleeding?

Female 48, pain lower left abdomen, happened last month then had a heavy bleed and clot tissue came out nothing till this month now 5 days late for menstral cycle and pain bad again today comes on suddenly and makes me light headed dizzy and feel as though i want to vomit, lasts all day then sems to go away?? last time stomach was distended don't feel that as bad this time? thanks