Masturbation, im confused!?

Ok sorry for the bad title but I hope you will help! well im a girl ( 13 ) and I do this weird thing ever since I was younger but now it has ummmm a better feeling? I would like put something from my arm to a pillow in between my legs and just squeeze them then unsqueezed them repeatedly. But recently there has been white stuff on my underwear and im sure it iisnt the stuff you get before your period because I have had my period for a wail and it smells different. I no this is kinda stupid to ask but is this my weird way of masturbating???