Has anyone taken norethisterone before?

Basically, the norethisterone is a progesterone. When you stop taking progesterone, after a couple of days you will probably have a "withdrawal bleed". This is how the contraceptive pill works, when you stop taking it the levels of progesterone in your body drop, which causes the withdrawal bleed. So what you are experiencing now is entirely normal. You may well experience a full "period" or you may just get some light spotting. Pregnancy is EXTREMELY unlikely, but if you are worried you could always do a test to put your mind at rest.