What Causes Irregularities In Menstruation?

i have this problem of irregular periods from the beginning.i have taken contraceptives several times bt when i take it becomes regular and again it stops once i stop taking contraceptives.i also have been taking homoeopathic for quite some time but it also never regularised my periods.now my periods are remaining absent for almosr 7to 8 months.i m getting married soon.i really dont know what to do.i also dont want to have any complications in getting pregnant.kindly suggest me what shall i do.......disha