Due date is off!

I'm supposed to be 8weeks, but my Doctor says, I probably ovulated a few days later than I thought, that makes me about 6+5 . Which makes my early pregnancy test after 8 days of Ovulation. He's a bit confused with my dates and so am I. I was so sure my ovulation happened early because I had peak the day before. And it slowly declined. Could I be wrong?

first positive was Nov. 26