Anyone had a scan and been told wrong gender

Have had a gender scan at 18 weeks and 20 week scan and got told at both there was no denying he was a boy. But can't help having a niggling feeling that I will still give birth to a girl, obviously it really wouldn't matter if he did turn out to be a she but I've brought so much blue stuff now lol. Just wanted to hear of any stories of having the different gender to what you were told to maybe but my mind either at ease or just make me aware that I could be right haha