In retrospect both my 13 week scans with DS 4 and now DD were really obvious so I can believe it. But it was never the angle, it was that DS had penis and nuts and DD had really long bright lines that just looked vag-y with nothing below and nothing really at the far end either, and when the tech did a bottom up shot, there was nothing there at all. I rem. with DS 4 thinking it HAD to be the umbilical cord - nope! I think the angles were all over the place though, because they were moving all the time.
Thanks you guys, I'm glad I'm not the only one struggling with this.
PS - The techs could tell too, even tho they are sworn to secrecy at my doc's office their demeanors gave it away both times.