I know exactly what you mean. They usually want to wait until 18-20 weeks... those elective ultrasounds at 14+ weeks are magical for those of us that are impatient lol. I'd be happy to look at the image and help you guess .
Oh darn! For my son, by 12 weeks it was obvious as it stuck straight up and was sizable. I kept hoping it would flatten out LOL. By 16 weeks you would definitely notice a little something sticking right up.