Suggest Treatment For Missed Periods While Not Being Pregnant

Hi Im 23 year old female and Ive never been pregnant, had irregular periods when

I was a teen, tryed birthcontrol pills and they stayed irregular, I ve had a cycst in my left ovry, it rupt... so it went to the hospital they said the cycst was gone and that they couldnt see anything else wrong , that everything was normal, now that im older my cicles dont really come anymore! the last time I had a period was about a year and a half ago... im not pregnant and im not on birth control.. I dont understand whats goin on please help!