If you are not breastfeeding... it COULD be your period. If not, I guess it could be lochia... but usually that ends around 1 month postpartum... and by now is would be scant- not heavy. Even if you are breastfeeding it isn't outside of the realm of possibility that it is your period.
If you are passing golf ball sized clots- or are in pain - or are soaking through a pad in two hours or less, call the doctor IMMEDIATELY! If you are bleeding like a period, but are not in pain... then talk to her or him at your postpartum appt. If you have already had your appt, then you should go ahead and call to at least talk to a nurse. They will give you advice to help you know if you need to come in, or if this IS just a period. In any case... keep a record of how long and approx how heavy your "flow" is. I would say that if you are bleeding at all after a total of 10 days MAX you need to get in asap. In fact... you should probably schedule an appt if you pass the week mark-
Really... this close to having your baby, it is best to be overcautious, about anything even remotely weird. Your doctor will be glad you were proactive!
-M.