Thanks for the query.
some amount of spotting can be seen for one week to ten days.
As your post abortion scan is normal there is no possibility of retained products.
So your bleeding could be because of hormonal
imbalance that is why your doctor might have kept you on contraceptive
In this after completion of 21 active pills you can have withdrawal bleeding while taking 7 inactive pills.
So that may be responsible for your present spotting, you don't worry continue the pills according to the schedule.