How well does Glow work for you ?

Hey ladies !

I need some help. I'm new to the glow app. I've only used it for 3 menstrual cycles. Every time Glow has been accurate in predicting when my period will start . But my period was suppose to start 6/25/17. It didn't come so I hit "my period is late" and it made the prediction to start today 7/4/17 any nothing. No symptoms or urine color change. I'm super scared because I want to be pregnant but I don't want to get excited. So my question is how accurate is Glow for you ? And what do you think about my situation? How long should I wait to take a test ?