I Need An Understanding

I have been using Glow for a very long time. Every since I logged my first month Glow has been spot on. Well, Wednesday Glow predicted that I would start my period. I didn't and I was hopeful that it might just be my time to have a child. When I logged Wednesday as my period being late it moved it to this Saturday for me to start my period. I took a pregnancy test today and it was negative. I am sad but does that mean that I will get my period on Saturday?