I remember my first couple grows, all antsy about figuring out the sex... trust me when I say if they are female or male you will know when it happens... females hairs start appearing all over the plant, and do so in a matter of 1-3 days, males 1 little ball appears and you start questioning if it is male or female then a day or two later and all of a sudden where there was one possible male ball there are 3 or more.
Just be patient the answer will come and you will know.