Help- nub theory!

[Donna0703]

Hi there I am new to all this! I am 13 weeks pregnant with my second baby and I have been looking at this nub theory and can not get my head around it!
I have spent hours looking on the internet and at the scan picture and am still none the wiser!
So here goes, any ideas?
Can any one point out what I should actually be looking at???
Thanks n advance!

I'd guess at a girl. I think its the grey bit at the end pointing out sideways from the bum.

I was thinking that, but it's so confusing!
I'm not even sure how true the nub theory is!
Thanks