Strictly female question....?

kso i have been geting really heavy discharge for about, 4 1/2 months. no spotting at all and when i go to the bathroom and i see the discharge in my panties theres a very bi like someone poured water on my back and it streamed into my panties. what can i do about this and when is my period coming? i am almost 13 about 4"10 (very short for my age)and well duh i am a girl.