Need information please

So I have PCOS. I missed my period last month. I was suppose to start November 22nd. I was tested at the Dr's a week and a half late and I wasnt pregnant. I know I most likely Didnt ovulate that month and that's why I missed my period... And then 2 days ago I decided to test... And BFP! Getting darker as well, ill post a pic of the night I tested, which was the night before last, and then the morning test today. But how will I know a due date if I missed my period last month?