Feeling nervous. .

This is my second pregnancy and I am 14 weeks today. I went for my first ultrasound at 8 weeks. During the ultrasound they saw fluid that went from the back of my baby's neck to about halfway down the spin. The doctor was concerned and sent me to see a specialist, who then did another ultrasound and saw the same thing. They ordered blood work and the maturity 21 test to look for any chromosome defect. I received the results and thankfully everything came back negative. I am so relieved that we recieved good news but I am still concerned. Has this ever happened to anyone? I need more hope that my baby will be happy and healthy. .