i was told the wrong gender of my baby?

So I got my ultrasound done a month ago (after many inconclusive ultrasounds of baby’s gender) and I was told it would be easy to find baby’s gender because I was 6 months along at that point - and it was a girl. Now I’m 7 months along and went for a check up ultrasound and the lady asked if I know the gender and I said yes!

So she goes on asking if it was my first and I said yes and she says “I remember when I had my first and it was a boy too!”

I feel quite upset? I don’t care what baby’s gender is but I just had a whole celebration and feel deceived. I’ve already bought many “girly” things.

I didnt (but should’ve) ask what the baby’s gender is.

Waiting to hear back from doctor, is it possible either of the ultrasounds could be wrong?