That is your body's way of keeping your vagina clean. Strange, but that's how it goes.
It's ok as long as it's not has a foul odor. If you can smell foul odor (like fishy smell) then you might have an infection. otherwise, it's ok..
Yes, this is completely normal. If I remember correctly, I started getting it a couple months before my period started for the first time. As long as it doesn't have a bad odor and you don't itch 'down there' you're fine. (If you ever do have those symptoms, just let your mom know, she'll know how to treat it or take you to the doctor.)
This is just yet another glorious perk to being a woman! lol