Mazal tov on the recent birth of your baby!
We are sorry to hear of the difficulty you are experiencing completing the clean days.
Once the bleeding subsides after insertion, you may perform a hefsek taharah as soon as possible.
However, despite the fact that the Mirena affects women differently, you should be prepared for the possibility that you may experience irregular staining for up to six months after insertion. Not all staining will render a woman niddah or invalidate the clean days, but given your extended staining experience with the mini pill, we are concerned that the Mirena may not be the right method for you at this point.
We recommend speaking to your doctor about switching to a regular combined birth control pill. At this point, when your milk supply should be well-established and your baby is ready to begin solids, it is safe for you and your baby. While regular birth control can affect your milk supply, any decrease can be compensated for by increasing both the length and frequency of feedings, as well as by supplementing with solids.
While regular birth control pills also have an adjustment period, irregular staining usually subsides within the first one or two cycles.
Please feel free to get back to us with any further questions.
B’hatzlacha!