When I was 14 years old in the month of December I was on my first period and after that every 3 months I was on my period. Not every 1 month but last year I was on my period every one month but now it's not regular at all like last time. This year at the very beginning of the month I was on my period but after that it stopped.
You should get checked by your doc to make sure there isn't anything else going on physically that is affecting your periods.