What Causes A Scanty Menstrual Period After An Embryo Transfer?

Ihave tried donor embryo transfer after being given injection lupride 0.5mg daily for 50 days and the donor embryo transfer failed i.e. hcg on day 14 after embryo transfer was only 33 which is then become 14 after 48 hrs. i got mensturation which is scanty i.e. ?good flow for oneday and scanty flow for 2 days which is unuisual for me. But after that the next mensturation doesnt start even after 34 days which is unusual for me (i used to have once in 28 days) what is the real problem?