Question about gender

Jessica • Mom of 2 boys, 1 girl🧒🏼👦🏼👦🏼26 years young. Engaged💝💍
I'm having another boy. I know that by having two ultrasounds to confirm. However, my mom can't help but think there might have been a mistake. She said I am carrying completely different this time than with my first born. I have different symptoms as well. Could she be right? Could I possibly be carrying a girl? I really hope not since everything I bought is blue.