What Causes Prolonged Delay In Periods After Having IVF?

Hi I went through IVF, it was failure, since I had only 4 good cells developed, I was not gone to second IVF. Since I was 37. After which my cyle seems to be very irregular, like I forcefully took promote November to menstruate as prescribed by doc. Yearly 2 times now it absolutely nothing. I am 41 now kindly suggest.