period lasting too long?

Hi, I'm 17, and have had regular periods for the most part since I was sixteen. Over the last couple of months, my period has moved a week later in the month. Usually, it lasts 5 days, 6 at best. Now, its been over a week, and I'm still bleeding lightly. I don't have any cramps or pain.

I was wondering if this was normal or should I be worried about something? How long should I wait before seeing the doctor?