Yes you can still find out. If you want to do the keepsake 3D sonograms they can find the baby's genitals for you and let you know! We're doing our 3D scan when I'm almost 30 weeks and we'll be able to confirm that our baby is a girl!
With my son, I was almost 30 weeks when I found out. (didn't have any u/s before that to determine the sex) I had a 3d/4d scan and is was very obvious! =) Sometimes babies just won't cooperate. Hopefully yours will next u/s you have. Good luck!