Fertile window? Cervical position

Candi • Baby one born March 2016! Was TTC for 20 months. Scar on my tummy is from surgery I had as a baby. Now TTC baby 2!
If your most fertile day is the day or so after you get a positive ovulation test, why does Glow mark the positive day as your most fertile day (33% chance of pregnancy)? 
Also, I may be feeling my cervix wrong. I feel it high and closed a lot but I'm not pregnant. I could be feeling the wrong part. Help!