Well the only time that you are going to find out if its a girl is when you start to flower. After a couple of weeks into flowering, little white hairs start to grow at every internode. If these hairs stay hairs, ITS A GIRL!!!! But if these hairs turn into little balls like nut sacks, its a boy Is the trunk of you plant thick enough to support the growth of buds? As for when to start flowering, 6 weeks is usually long enough to veg then happy flowering!!!