Things happen before period

GuinevereVivi

For me, I am like this:

Sometimes, I can feel pain of my breast ;

Sometimes, I want to have sex like hell right some days before period...

These are the hint for me when I know my period is coming

But why not all the time I feel like this ? Because I can know when my period comes

Or is any there ways that I can know ? Or maybe something about vagina?