How accurate is Glow?

Amanda
I have been keeping up with glow for several months (4-5) I used it mainly to track my period and fertility window. It took a few months for glow to get my predicted period right. This month I was suppose to start on December 26th and it came and went. Logically I marked the prompt "period hasn't started", glow recalculated for me to start on December 26th. 
I was very anxious more than usual. For the past few weeks I noticed my breast were sore and I had cramps like my period was coming. My "DOT" didn't come today and I thought only way to know for sure is a home pregnancy test. Welp, first was positive. Second I had to buy a digital to convince myself a little more which was positive. Just scheduled a blood test with my primary doctor. 
This will be my first. I've been with my boyfriend for eight years, his first as well. I'm extremely nervous, I'm a Registred Nurse so I know the first few weeks months processing a pregnancy can be filled with lots of anxiety. 
I haven't told anyone. Except the people reading this. Who/when should I tell anyone?