Does Megestrol Tablets Cause Irregular Menstruation?

I've been taking Megestrol 20mg for about a week now, i'm supposed to take it pre-op for my Essure procedure to thin the lining of the uterus. my period is now 4 days late, aside from being on Megestrol i'm also on dilatlin both harmful to fetuses, however i do not believe i am pregnant i've taken tests. Could the Megestrol have effected my menstrual cycle after only taking it for a week? It felt as though i was getting my period but it never came?