Question about CM.?

So I have a curious question. I have never really payed attention to my cervical mucus and the last couple days supposed (today is supposed to be my last fertile window) I have been really dry down there. When I wipe that is. I don't have any issues when it comes to sex. Except tmi a little to wet sometimes. What could be going on with my body. The 17th was supposed to be my most fertile day.