My period has changed since I started taking Follistim. My periods used to last 5-7 days and now I have a period for 3 days. By the fourth day I have no spotting at all. The length between my periods are longer now too. My periods used to be 28-30 days. Now it is more like 35 days between periods. Also, my periods are way more painful than before. My RE said it has to do with me making several eggs and when they do not get fertilized they get discarded during my AF, which can be painful. A couple months the pain was almost as bad as the labor pains I had with my son.