Help me solve this riddle!

I’m trying to figure out how far along I am. I thought I was 6 weeks 3 days, based off my lmp of nov 20th, when I went to the doctors yesterday for my first scan. But my doctor stated that she thought I could be earlier than that based off what we saw, only the gestational

sac and the yolk sac. I had been tracking my ovulation and I know I ovulated in December 6th. We BD’d in December 6,7 and 11. I can’t figure out when I conceived. I just want to figure out my due date. It’s driving me crazy that I have to wait 4 more weeks to find out. someone help!!!