@Paranoidkaty I've been reading your posts and you remind me a lot of myself in my pregnancy with my little boy. I'd had two miscarriages before him and was plagued by anxiety during my pregnancy. My combined screening wasn't high risk, it was 1:1300 but that seemed high compared to my friends who had all got 1:10,000 etc... I did loads of reading and knew that the combined test didn't detect all cases of T21 and became convinced that I was in that group. Also his NT was 2.7mm which I convinced myself was high. At my 2 weeks scan the femur bone was in the 30% percentile which I took as another 'sign'.
I had private scans at 28 weeks and 36 weeks and despite them showing the femur length to now be in the 70th percentile I still worried right up until I had my little boy. I was really convinced I was going to be in that missed percentage. I wasn't, my little boy doesn't have T21 and I feel so sad that I spoilt so much of my pregnancy worrying.
For me, I think my miscarriages had left me believing that something always had to go wrong for me. I didn't get any help for my anxiety when I was pregnant, but I got counselling before this pregnancy (after I'd had another miscarriage) and it's helped hugely. Techniques like mindfulness have helped me better control intrusive and obsessive thoughts.
This time I did actually get a high risk result on my combined screening but had a low risk NIPT test. Of course it's entered my head that it could be a false negative but I'm determined this time not to let those thoughts take over my pregnancy. Every time the thought of 'what if it's wrong?' Pops in my head - I tell myself if I should happen to be in that really minute (tiny, tiny) group who had a false negative NIPT test, then I will just have to deal with it, simple as that.
I really hope that you manage to enjoy your pregnancy and put some of the worrying to one side. I know it's so, so hard. I definitely recommend taking any help you're offered and also trying things like CBT and mindfulness too.