NT reading

My 12 week scan baby was measuring at 13 weeks exactly which I thought he would due to the dates, the NT screening came back at 2.6mm, the bloods results came back as very low risk, the risk was 1 in 20000! Which we've been told that's an exceptionally low risk reading! But at 20 weeks scan baby was 20 weeks and 2 days and his femur was 19 weeks and 1 day. I know having a short femur can be an indication of abnormalities. I will be having growth scans due to him being just below the 10th percentile, which can also be a sign of abnormalities. I'm just really stressed. His brain, heart, kidneys and everything was perfect. His profile was perfect, all fingers and toes present but I just cannot shift this worry! He even has hair on his head already but something is just bugging me really bad