Can my ultrasounds be wrong?

Tamara
Can you ladies please give me some reassurance?
My EDD: August 5th
Ultrasound at 9w 6d: exact w/ period
Ultrasound at 14w 2d: exact w/ period 
Period/bleeding: October 29th - 3rd
Conception date: November 12-14th
Is there anyway I could have conceived from intercourse from October 7th? I just need a peace of mind..