If you are on the pill, check with your doc and see if you can take them continuously (i.e., avoid the placebo pills). My doc has prescribed them that way for me for years because of horrid periods. How close in time is the ride? Could you see your doc before then? He or she might have some other options for you.(
This is what I do.
Grits
2010 Trek 5.2 Madone WSD, SI Diva Gel Flow
2002 Terry Classic, Terry Liberator
2013 Volagi Viaje
2002 LeMond Tete de Course rebuild/"The Chimaera"
2012 Scott Contessa Foil with Dura-Ace
2011? budget "Takara Kabuto" Single Speed/Fixie "The Bumblebee"
1999 Santana Team Ti 700 tandem/"Silver Streak"