Ok so I've had the <a href="https://play.google.com/store/apps/details?id=com.glow.android">glow app</a> for a year. I'm trying to conceive... Every single month my period has been correct and came on time with the app...last month the app said my period would end on the 19th but it didn't end til the 21st ..so I went back on the app and change my info and length of my period for two days longer, the app says my period should start today (Sunday) and if I didn't change it the app would have said my period was due on Friday..is it safe to say I'm two days late or wait to see if I get it today before I waist money on a test that keeps coming back negative.