irregular menstrual period

hello, i am 19 years old and a little preocupied. i have always had a regular menstruation until this last one. my period was a week early, the first 3 days it was really light, on the fourth day it came heavy with big blood clots. my period usually last for 5 days but this last one was more than 8 days long. after my period ended i have been getting a brownish redish discharge and i have had it for 3 weeks. what is wrong