All three of my girls hid like that..We only get one at 20 wks too with the military, unlesss something is wrong
so my husbadn and I went to this place that they have students do it so they can learn and then the dr will come in and tell you everything so the student can listen and see if they did it right, it only cost us 20$ and the tape is free if you take a blank one, if not it is like an extra 3
maybe you can find something like that to go to and try again to find out the sex
the girls have three dark lines that show up for the privates, never seen a boys though!!!!