I have always had irregular periods, ever since I first got them when I was 13. I have been on birth control since I was a teen so now I somewhat control them myself, but not entirely - if I skip too many periods using birth control I will eventually just get my period anyway. The periods I have been off birth control (for many months last year, for instance) I have always had irregular periods and it was the same before I started it. I don't think it's anything to worry about.