Mazal tov on the birth of your baby!
It is very common for postpartum bleeding to come and go in waves, much as you have experienced. However, if this happens yet again, it would be reasonable to consult with your gynecologist.
If you did become niddah again the morning after mikveh, then you will have to wait the five days and count another set of seven clean days. If you haven't had a full fledged flow, but rather heavy staining (also common postpartum), then it is possible that you are not in fact in niddah. Please see our articles "Stains" and "Toilet Paper" for more information and please get back to us with any follow up questions.
Doctor permitting, you might also find it helpful to take bioflavonoids (1000 mg three times a day) or ibuprofen during this period to reduce staining.
Please write back with any further questions.