I’m 14 now and i got it a few months ago when i was 13. i had told my friends that i already had it because most of them had.
i’m in year 9, which is the first year of high school, and it was the day of my first exams. i was feeling sick with nerves because i like to do well. in the middle of the english exam the rover came around so i was allowed to go to the bathroom… and i discovered that i had my period!
i usually carry pads in my bag but i used a different bag that day so i had to use TP. the one day i didn’t have pads WOULD be the day i got my period lol 
i told my mum that evening and it was all gud. i’m quite skinny so they only last for about 4 days and i never get cramps