Sad/angry!

At my 13th week apt the ultrasound tech told me by my 16th week ultrasound she would be able to tell me what the twins genders were and I had my appointment yesterday and she barely even tried to look. She said she rather wait till my 20th week scan. I was so sad and angry because she got me and my fiancé’s hopes up and we didn’t get to find out. We have nothing for the babies yet and it’s stressing me out that I have to wait another four weeks to find out. Should I just schedule a gender reveal ultrasound at another place? I know a place where I went with my first born so we might go there!