Dear moms, who at what gestational age found out the baby's sex? Did i…

Dear moms, who at what gestational age found out the baby's sex? Did it match up? At exactly 16 weeks, I had an ultrasound (by appointment), the doctor didn't want to say anything, she said that the baby is covering with legs and nothing can be seen. Meanwhile, I saw something similar online, something like a girl. So I told the sonographer, it seems like a girl, she said yes, it looks like a girl but not for sure because the legs are covered. So, did you have any experience where you were wrong about the sex at early stages? And did it match up?