Due date?!?

I recently found out I'm pregnant with my second baby! (Take that PCOS!!) Anyways, just curious about figuring out what my due date might be. Would you go by last menstrual period, which was a full 5 days, or by possible implantaion bleeding, which was only one day and very light. The implantion bleeding was two weeks after my last period ended. Ultrasound is in two days but I'm very anxious to know.