6 and 7 week ultrasound. on dec 9th i was 7 weeks. due date july 28th is there anyway possible i could have gotten pregnant oct 12th?

No: October 12 would have been one menstrual cycle too early. With a july 28 due date, the baby began with the next ovulation, in the november cycle. Life is never exact, but this is as good as the estimates get.

Unlikely: Using an obstetrical calculator, if the sonographic estimated due date is july 28, 2014, then your estimated date of conception was nov 4, 2013, all other things being equal.