LMP & Due Date is off a week difference? Help

(Question 1:)Ok starting back from October 2017. October 30th I had unprotected sex, October 31 I took a take action (off brand of the plan b) my period come down really heavy on November 10th lasted 4-5 days. On November 22 I had unprotected sex but he pull out before he even ejaculated , on November 23rd I began bleeding for 3 days. I had bleeding twice I. The same month? Did the 2 periods come from the morning after pill?

(Question 2) my expected period was suppose to be December 10 2017 but I didn’t receive it until December 19th. I haven’t seen my period since then December 19th. With the due date of September 17 2018 from what the ultrasound is saying . But if you type in the due date it’s saying I had a period December 10 when i had it December 19? My due date is really supposed to be September 25th a week different from the ultrasound date, my question is when was likely I conceived? Is this normal? I’m just worried my baby may be delivered by c-section too early?