If your periods have become lighter and is now brownish black, it is no cause for worry. There is no need to see the doctor again. Periods are likely to be a little different than your usual, once you have taken hormones.
Period irregularities like yours, occurs once in a while, due to hormonal
disturbances, and then gradually settle down. If it is a one off, do not worry. Hopefully your successive periods will be normal.