ANDY'S ANSWER: It is not unusual for a girl to start getting a white discharge between 6 months to 2 years before her first period, and it definitely is a sign of puberty. It means your period will soon be coming along. Even after your period starts, it's very common for girls to continue to have this discharge. It is a way for the vagina ti cleanse itself.
If it makes you feel uncomfortable, try wearing pantiliners every day. They are very thin and discrete. They will keep your undies dry and will give you some ready protection for when your periods do come.