HELP!

Ash • CNA, 19, ttc #1
So I am supposed to get baptized this Sunday and I'm supposed to start my period today (Saturday) and normally I would have worn a tampon then just changed right after (it's a lake so I don't want to get an infection) but there is my pastors sisters house but she isn't allowing anyone inside so basically I have no where to even change out of my wet clothes. Please help!