Gender confusion

Angel
I had an ultrasound on August 9th at 21 weeks and 5 days. So this one was to see if baby had all body parts and possibly see what the baby will be. (Which is what I was excited for). Baby is healthy but when it got to the gender the guy seem like he couldn't tell and yes I can't blame him because baby was moving alot. But the thing that's bothering me is that at first he said girl then later he came back around to check again and said "well maybe it could be a boy" he was using the hamburger or hot dog method. I'm happy I got to see how big the baby is now but I'm really broken that he didn't give me one set answer I've been waiting for this day since I was 5 weeks. I can't see the baby again til my 3rd trimester and it would really help if I knew what it was for sure I can't help but to feel disappointed and crabby about this. Any suggestions on what I can do to get a for sure gender?