Yucky Vaginal Discharge?

Hey so I am thirteen years old and I haven't got my period. I am very tall and skinny with boobs, pubic hair, the real deal I just haven't got my period. For a few years now I have had a gross discharge which always comes out of my vagina. It used to be yellow but since puberty it has gone white and sticky. It could just be cum but I don't know. Advice?