bleeding for 8 days in a row (so far)

i started bleeding 8 days ago my period was supposed to start september 1st but i started bleeding august 23rd. at first i thought it could be an early period but my periods never last 7 days any other time. blood is coming out very brown/black and a sticky substance. my regular AF is very bright red and very heavy the first couple days and then slows down. this blood is enough for a pad but not going into the pad very deep at all and remained consistent amounts the whole time. i went to the hospital yesterday and everything came back okay i have to make another appt w/ my GYN since i'm still bleeding and it doesn't seem to be going away. does anyone know what i can expect? has this happened to anybody else before? if so what caused?