Not in a relationship & now pregnant

Intercourse October 7th (protected) 
Period October 29th - November 3rd
Intercourse October 31st & November 14th (unprotected) - current boyfriend 
Ultrasounds match with conception and period date.. 
EDD: August 5th
Is it possible that I could have conceived in October at all and for the ultrasound to be off a month?
My doctor said no but it's still on my nerves