I think its the gestation that is making people lean blue, if a nub is going to rise its usually in the late part of week 11 early part of week 12 and there is some change between the 11 week shot and 12 week shot which made me think it could be rising.
Just looked at your other thread and there are a few images where there is a slight angle - my babes nub was poker straight on the dvd at 12+1 but even then it was too early to say it was def a girl. If you were using opk's its probably more likely your dates are more accurate than the u/s dates which gave me a boy lean but it was just a lean - if you'd been 13 weeks plus i would have said girl it just looks like it could turn but then i have seen some boy looking nubs turn out to be girls and vice versa its not 100% so please don't give up hope, especially if you swayed as its not a true boy nub either