NT more than 2.5mm is alr off the range. I think it is better to quickly do NIPT test (don't go for oscar test, it will give u more nightmares due to its degree of inaccuracy) for accurate result. These info can be very haunting and leaves one paranoid, moreover down syndrome can happen on any # of pregnancy, if you can't get over it, should quickly do the test for peace of mind. I understand it's tough to hear these info, I cried upon my oscar test result too. Hope everything turns out well for u & bb.. all the best!
Valerie Lau