This is a picture taken from an old BYC post of a four month old silkie rooster that was for sale. If you compare this bird with yours…quite a difference.
Posted by "dozen chickens" in 2008
At five months she is almost old enough to lay eggs. I believe, if a rooster, there would be little doubt by now. While the crest doesn't look right, everything else is hen. I assume there is no crowing. My silkie roosters were well developed by five months.