i recall from the school -biology said, when female reaches the teenage.. the hormone will build up and then period will come. For a health person the ovary will fully developed and laid egg simiulatenous.. however, for some people, ovary not fully function.. like me, even i have period everymonth, but only have egg in alternative month, as one of my ovary not producing egg... so of course, end up less chance of getting pregnant.
suggest you go to see the doctor to have thorough check up on the ovary..