Doctor said boy at 10w4d scan, technician says girl at 20w scan?

I am now 20 weeks into my pregnancy. When I had my first scan at 10w4d, the doctor excitedly told me that I am having a boy. We could definitely see something dangling between the legs when the baby was moving around. It was triangular, and pointed downward, about 1/5th the size of each leg. The doctor even asked the nurse in the room, and the three of us thought it definitely was a boy. The baby was lying with legs spread wide. I had my 20w scan last friday, and even though I was able to see all organs, except the genetilia, the technician confirmed its a girl!! She even marked the same on the copy that she gave us. She showed me the labia (which was not clear to me) and said that I am definitely having a girl!! Let me be honest...I was little disappointed, because I was dreaming of a boy since my first scan. Do you think a lady doctor with 23 years of experience can make a mistake at the first scan? Whom should I trust? Please help.