Hello, I would be happy to assist you.
You can go ahead and start your Primolut now, but usually it is too late once the bleeding begins.
I would recommend you try calling your doctor and asking for traditional birth control. These will contain estrogen and progesterone (Primolut is progesterone only). The increase in estrogen will help turn your period off. Whereas the progesterone will help prevent it from starting, but once it starts it's usually too late.
I wish you the best. If you have no further questions, please rate my answer. Thank you.