Nuchal Translucency Test

Monday I had my 2nd sonogram at 12 weeks, 4 days. They did a nuchal translucency test (doctor didn't mention if it was optional or not when scheduled) and this was my second ultrasound. My first one was at 5 weeks and based on measurements they moved my due date from July 9th to July 14th. No one ever mentioned during the blood work for this you can find out the baby's gender, I'm dying to know, is it too late to find out now? More importantly, here's what concerned us, during the ultrasound the tech didn't say a word to us, she just kept remeasuring what appeared to be the spine/back of the neck and bouncing the thing on my belly really concentrating and trying to get the baby to move. It really freaked us out but when we left she gave us some photos, said the baby was measuring for the July 14th due date and any results would be in a few weeks unless something is wrong they may call sooner. Two days later I got a call saying everything looked completely fine with the measurements and the blood work they took and there is a very, very low chance of any issues, however, she said the fluid behind the neck measured 2.9 which is a little high and anything over 2.5 they like to review again at 18 weeks. So they are scheduling another ultrasound. Has anyone else experienced this? Should we be worried? Here's a photo of our lil peanut.