Med help has a tracker that you can use!
If you are not sexually active, then you probably have nothing to worry about. Your period can remain inconsistent throughout your pre-teens and teens. Then when you're an adult, it can still be off sometimes just due to stress, sickness, diet, etc. Speak with your doctor (if you're not comfortable talking to your parents) about your cycles. They will more than likely ask you to track your period on a calendar. This is great to do because most doctor's appointments ask you when was the first day of your last period was, and it's nice to be able to look at your calendar really fast and give an accurate answer.
Hi and welcome. Irregular periods are very normal at this age. I do recommend that you talk to your mom about these things as that is what she is there for. You'll get better answers and concern from your mom than any stranger on the internet. good luck hon