Need opinions

A
I went and had an elective ultrasound done at 15weeks which was 6/27. They told me a girl and I am thrilled!! But I am beyond petrified that they are wrong because the baby is still small, can any please help me and guess with skull theory? I would love a boy I am not being ungrateful I just horrible anxiety and my anatomy scan is not for another 5 weeks. Thank you!