Late ovulation cd 26 got pregnant, due date?

Madison

So I got a positive opk on cycle day 25-26 I usually ovulate cd 20 or 21. I did get pregnant on this cycle, but I’m wondering when my due date will be? I go to the Dr Tuesday for my first appointment and they told me that I will be 7-8 weeks, but I went to a smaller ultrasound clinic this week and they told me I am measuring 4-5 weeks very early, which makes sense for me ovulating only 3 weeks ago! How will my due date and weeks be calculated when I ovulated so late? Based on my LMP baby would be 7 weeks and some change, but I am not actually that far