Happened to me when I was twelve. Took me several years to get regular. It's normal.
probably it doesn't mean much. At your age, in the early teen years, being irregular is very common and normal. Your hormones are just getting going! So, try to track it (you can use MyCycles, the app, here at MedHelp. Go to above tool bar and click on Health Tools to find it)--- but don't worry if it is irregular for a while. If you are not sexually active, this shouldn't be a problem. You may start to see signs that it is coming if you get PMS symptoms. The app will help you notice this. Hang in there . . .