Has Glow ever gotten your period wrong?

Whitney
I found out last Wednesday I'm expecting! I'm now 3 weeks and 5 days. According to Glow, I have missed my period this month but according to other websites I'm not supposed to have next period until tomorrow? Glow has always been right on the money with my periods.. I've always been very regular and on time. Help??! I have a 28 day cycle.