hi i had gone through your query and understand your concerns.
-it is normal for you due to hormones adjustment from secondary amenorrhoea to appearance of menses.
is the major hormone during lactation
and when it decreed or completely stopped,then produce oestogen and progestreon hormones .
-due to sudden change in hormones may produce this condition and it will be normal simultaneously without any treatment.
I hope this is helpful for you, thank you