At the outset I must congratulate on your grit: to breast feed your baby for at least for one year. It is not only the responsibility of the medical filed, but entire civil society to support such mothers.
We will divide your question into two parts?
The problems with norethisterone
Ofcourse internet web pages will through several complications. For practical purposes you divide them into minor and major. Major one which disturb your daily routine. Minor ones you can ignore. You may not experience all of them. So go through the product insert, there they would have mentioned major complication : for example breathlessness, severe cough
, severe pain
in the legs: abdominal pain
severe. then only you need to stop the medicine. This the prescribing doctor also would have indicated.
I would like to see the problem from baby's need.
This child deserves mothers milk and that has to be encouraged. What are the side effects of the drug in breast milk? The doses you are taking should not affect the baby. High doses, yes, can affect breast milk production.
In medicine, there is what is called benefit versus risk ratio. Breast feeding is beneficial.
When we seek for evidence, the transfer of Norethisterone was just 10% ie only 10% of the drug got transferred from mothers blood to her breast milk was only percent. How much this will affect the baby, we can take a chance.
Lastly this drug you are not going to take for a long time.
As a pediatrician
I will support your aim of breast feeding
don't hesistate post again in the public forum on this topic