Did I ovulate late?

I know for a fact that my last period was Oct 17. Which, based on a 28-day cycle would have put me ovulating on Oct 31. I am currently pregnant and due Aug 3rd. Which coincides with a last period of Oct 28 and ovulation on Nov 11. Going by the date of Oct 17, that I know for sure was my last, I would be due July 24th. I have had 3 ultrasounds so far. One being in December and I was 6w2d and that coincides with an August 3rd due date. Then I had one in January that put me at 10w2d and that one also coincides with an Aug 3 due date. So, is it possible that I just ovulated late and got pregnant several days after I thought I did?