Confused

So i was rear ended a week ago yesterday. I was sent for an emergency ultrasound last Wednesday and we found out baby is measuring 2 weeks ahead and the head is measuring 4 weeks ahead. I had another ultrasound today to make sure the baby was still doing good. when she was looking at cervix/ baby's head she kept asking your over 35 weeks right? has anyone had this happen before? First thing I thought of is maybe I'm dilating because I've been very crampy and braxton hicks are becoming painful.