Just tell your Mum and she will help you from their, don't worry all girls start theirs from around the ages 9 to about 15 every girl is different, and it's not that bad as every one says it is and your first period should be light and short so it's not that bad the first time.
P.S. If your worried about starting it at school ask your mum if she could buy you emergency pads that you could keep in your back pack.
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