My period always comes like every 3-5 months and I'm worried something is wrong. I'm barely 13. I'm not sexually active and I never have been. When I went to get my physical for sports I told my Dr about it. She said it was normal for some girls when they start but I started at 10 and it still hasn't come regularly. What should I do?

When your doctor said it's normal when you start, she meant for any amount of time - months or years. Girls can start younger than you did (not much - 10 is young) but also well into the teens, without being abnormal at all. Thank your lucky stars yours are months apart for now, and don't worry. Google menstruation if you want, and see all the statistics and discussions.