Just need clarification

Kind of long, please bear with me :) 

I was supposed to be 18w2d based on my due date but I was measuring 16w4d

(Sadly I missed my first ultrasound because my oldest got sick and I couldn't reschedule in the time frame) so the ultrasound tech, who was very great about all of it, said she would take all the measurements and see if she could tell me anything. Well of course the baby had it's legs crossed and wouldn't help us and since I was measuring behind she wouldn't give me a real definite answer. 

She said my doctor would make the definite call and it wasn't up to her but the machine said based on how the baby was measuring that they would change my due date by 2 weeks (to March 24th) and I would get another scan for gender....now here's where I am confused. She said based on her opinion, she would said 70-75% it was a girl, cause she saw no boy parts that she could tell but she couldn't see definite girl parts either...but I have seen people with clear pictures at 16 weeks of gender...so do I go off her opinion or wait til the next scan in a month (mind you there wasn't anything clearly sticking out like a boy or anything but it moved around a lot and we didn't see either clear signs....?