I've been using Glow for about 2 months and it had been accurate about my period so far...Glow said my period was suppose to start Sunday (7/26) & since Thursday I've been having period symptoms (headache, cramps, fatigue) so Saturday I took a pregnancy test and it was negative but I still have not started my period....I'm excited nervous anxious...when should I retest or should I even retest!?