HELP!!!

Chloe • |-/
So on Friday, my school is having a field day thingi were we HAVE to do all these activities and junk but I'm gonna get my period!!! It started on Sunday but my flow is REALLY heavy this time so I bleed through 2 pairs of underwear AND a pad:( I can't wear a sweatshirt around my waist cuz we probably can't cause we'll be doing a ton of activities!!!
Any ideas?!!?!