You can always ask for another one based on the fact that the tech has you concerned about things that maybe he shoudn't have brought up. I don't think a tech should have said girl when gender can not be confirmed until after a certain time. And here they are not allowed to bring up a concern of Downs' to you and can only tell your Dr. that they need to do future scans for several weeks.
Tell your Dr that the tech was very unprofessional and upset you a lot and you want to confirm a healthy baby!