Ovulation & Ovulation Tests

I'm still getting the hang of using ovulation tests. A little background on me, last month I did have a positive ovulation test on the first day of my predicted fertile week so glow adjusted, my cycle ended up being irregular in November so glow readjusted again. My fertile week for December according to glow is 12/13-12/19, here's my ovulation tests so far. Tomorrow is supposed to be my most fertile day. I'm thinking I ovulated sooner than the 13th and started testing too late :/ Thoughts anyone? Anyone get pregnant and not have a positive ovulation test?