What Causes Lack Of Periods Since One Year In A 15 Years Old?

Hi, I m 15, female . I haven t had a period for almost a year, I ve not had sex ... And I would like to know why I m not having periods.. I ve looked up things , but there s possibly that it can be any of them , I haven t been to the doctor in a few years , I should have been long time ago, but I am scheduling an appointment soon. I just want to know if any of this May affect my future on having kids someday as well , like if something isn t working properly in my body ... I don t know .. But I find it odd , that I ve had periods before and all the sudden I don t have them, then get them randomly .. I don t take any meds for anything , help . Thanks.