Due date confusion

Hey guys,

So I’m really confused with figuring out due date. My last AF started on 1/11. I got my first positive on 2/18. However on 2/16 I was still getting negatives. According to all the due date calculators, I’m 6+2 with a due date of 10/18.

Do y’all think this could be right even with me still getting negatives until 2/18. I feel like if I was that far along I would have been getting positives earlier than I did.

Thank you so much ❤️