Pregnancy Scare

Marly • Mommy and engaged.
I actually find myself in a very strange situation. My period has never truly been normal and on schedule but for the past couple months, it has at least been only a day or two late/early. However, it's been a week now and still nothing. I keep telling myself I can't be pregnant because me and my SO had sex in early September, I got my period towards the end of September and the only other time we had sex was last Sunday which is the day GLOW said my period would begin. My SO and I are very open about these sorts of things and he is excited to consider the sheer thought of a baby but I am truly freaking out. I know way too much about biology and anatomy to even be thinking this way but is there a possibility that I might be pregnant?