I was lucky last year not to have my period during the con. And I was surprised since normally when I'm excited for something like Kumoricon, it starts up and I'm like:
"FUUUUUUU MOTHER NATURE I'MA GONNA KILL JOOOOOO". (And last year it was funny that my friend started hers on Day 0, then my other friend started hers about an hour later, THEN my sister started hers seriously right after that. They all looked at me waiting for mine to start, and it never did. >:3)
For me, my troubles are these: VERY heavy bleeding, and I experience really bad cramps to the point I'm in tears, and I take pain relievers too. It still doesn't do much to ease them. I'm not really moody during my monthly, but I'm normally exhausted and just want to hide in my room til it's all over. =/ So I REALLY hope mine doesn't start during the con this year, and if it does, it will suck. But luckily, I'm in a simple cosplay this year. =D