What Causes Termination In Periods?

Hello, I usually have my periods after 45 days, I have been to doctor and 3 months took course of gynera pill and after stopping the pills it is back to same old 45 days. I am married and doctor suggested not to worry and he will advise some medication when we are ready for kid. Now my problem is, I didnt have my period from 2 months, mine last was on 17th April. I am not pregnant as well. I went to doctor to get periods and he suggested to have norethisterone twice a day, 7 days. but i could not continue after two days. its been 5 days I discontinued the norethisterone tablets. Please suggest if I want the periods to come in two days what to do or /also advise if it is ok to post pone the periods till August.