15 week ultrasound

Cristy • Wife.Mother.MakeUp
I had an ultrasound today at 15weeks exactly.   I saw what I thought was a penis.  My dr said if he had to guess he would def guess boy.  We couldn't get a clear pic but I was wondering how accurate it woud be this early?  I mean I def saw something poking out lol we find out for sure in 3 weeks so I was just wondering.