Help!

My last period was May 14th. Putting my fertility window around Memorial Day weekend. I was sexually assaulted June 5th. I took plan b June 6th. I've had a steady bf for almost a year now. We had sex all Memorial Day weekend. And also the day after the assault and then a few more days after that. From my last period date I should be 7 weeks. I went in for my first ultrasound today and was measured at 5w6d. Any help??