Suggest Remedy For Irregular Menstruation

Hi I am 20 yrs old and never have done sex. .my period dates are usually up I mean they rarely come on time. .but in this month of March I didn t had my periods and taking regestrone two tablets at night after dinner can I know when will I get my periods? ? And can I get periods while having regestrone ?? M having it for 5 days in which today is third day of my dosage ?? And what are the symptoms that regestrone is working inside I mean my having little abdominal pain but no periods yet??