Based from the information it seems like the discharge is due to prolactin
hormone which helps for lactation
after delivery but since you had miscarriage
the milk is not used by the baby's sucking hence you are seeing the discharge by pressing breasts.
I would like you to go and see your gynecologist in a bring it to his/her notice and they will prescribe medication to stop the prolactin hormone release , which in turn will solve the issues of discharge.
hope it helps.