15 DPO, BFN. When do I test again?

Katie • Our first is so fun - let`s have another!
I'm going to Chicago tomorrow for  a girls weekend with my mom and sisters.  
​Unfortunately, I'm going to have to pack a bunch of supplies in case AF shows.  But, they want to go out and have some wine and whatnot.  
They know we're TTC, and that I expected AF yesterday.  I really want to enjoy girls weekend with them - but I feel like I'll spend the entire time obsessing!