What Causes Irregular Periods And Abdominal Cramps?

I have cyst broblem since 2000. I am 40 yrs old Maldivian. At the very early time When period time I have great pain all over my stomach and abdoman. Now adays there is pain and long time take when get period. When the inter course time ther is a pain also. Monthly Period is regular but taking long period , not much bleeding but strains are there. First two three day haeavy bleeding is there.