Conception question

Michelle
So at my first appointment I got a dating ultrasound which put me at 8 weeks, 3 days ( this was exactly a week ago). We counted it out and that would put the date of conception on July 25. The first day of my last period was July 26. Just sounds weird that I could conceive the day before my period. And that would mean I got my BFP at exactly 4 weeks. Can you ovulate the day before your period. Or did we just get lucky on one of those slight chance days.