What is this white substance

I'm fourteen and I'm a virgin and recently, ive had this unusual white sticky substance coming out of my vagina. It doesn't resemble puss, so I don't think it's a yeast infection. I'm just really unsure what it is and how can I stop it from happening because now it's staining my underwear. Does this happen to anyone else, and if so, do you know what is it or if it's a normal thing?