It’s hard to sex at that age but you can give it a go.
Press your finger down the vent area just in front of the anus. the area will protrude. A doe will display a slit. Each side of the slit will be pink. Whereas A buck, will display, if less than 5 weeks old, a blunt white tube without a line in the center. It will not have pink traversing either side of a center line.
I used to be able to sex 'em at this age, but now, I find it too hard to get my eyes to focus on something so small (note to self - get new glasses!). At this age, he has a dot, and she has a dash. Another thing to look at is the space between the rectum and the urethra - there is almost no space at all with the doe, while the little buck has a noticeable space (about 1/8 of an inch) between the two.