Your period should be around 7 days or so, you shouldn't be having a period lasting longer than 2 weeks. Your period should last just long enough to shed the lining of your uterus. So since it is lasting longer you should really go to a doctor. If you aren't sexually active I'll assume you aren't on a birth control, because birth control tends to help with cramping and irregular periods. So it might be something simple that can be fixed with a birth control, but you won't know until you go to a doctor.