I started mine when I was 11, shortly after my mom died. I knew what a period was, but I didn't really get what was going on when mine started. I changed my underwear about five times before it clicked, and I asked my grandma for a "sanitary napkin" (I was really, really embarrassed).

As for myths, my ex claimed he could smell when a woman was menstruating... and my cousin was absolutely convinced that women only got pregnant while on their periods, sort of like dogs in heat. I tried and tried to explain the whole process of ovulation to her, but she wouldn't believe me.