PLEASE HELP!

Nevaeh
I'm a first time mom and don't know what to believe. I had my first gender scan at 15 weeks it read girl then I had a second one done at 18 weeks and that one read boy! I don't want to start buying boy stuff and the baby being a girl...HELP!
BTW... The second ultrasound tech said she has been doing this 30 years and she's 99.9% right all the time.