How Long Can Norethisterone Be Used?

How long can I use nerothisterone? I have always known that the recommended period for use of Nerothisterone is no more than 21 days in a case, for example, involving vaginal bleeding. However, early this year my wife was put on Oralcon F, a hormonal contraceptive to stop her periods altogether as she was in extreme pain due to endometriosis. For a while, this helped. Her periods stopped and she began to enjoy a better measure of life. In April, the situation changed. She began to bleed through her vagina and experience severe momentary pains. When we visited a doctor we had a scan which revealed that her uterus had thickened. A DNC was recommended. Post that procedure, the pain was significant. We were advised to take nerotheristone to help the bleeding. In the preliminary stages, this didn t help as she continued bleeding. We were advised to increase the dosage from 2 times daily to 3 times daily. After a couple of weeks, the pain and bleeding began to subside and had to discontinue the nerothisterone as she was past the 21 days. 4 days after discontinuing the nerothisterone , the bleeding and pain came back. Please advise. What can be done? Should she continue the nerothisterone? Can it be taken beyond 21 days? Should she stop the Oralcon F?