Hi Dr, I Have Not Seen My Periods For Almost

Hi Dr, I have not seen my periods for almost 2 years now and I am not pregnant. had cysts removed and another laparascopy to check if tubes were blocked and also been taking Provera for the periods but never came out of it.
besides PCOS, What else could be the cause of periods not coming at all and what must I do to get my periods back? Is there a permanent solution to this as I am tired now and want solution to this problem once and for all?