Hi, Emergency contraceptives carry higher doses of hormones enough to disrupt the normal hormonal milieu of the body. Thus, they cause a breakthrough bleeding within a week after intake and also delay the next natural period by about a week or two. Since you have taken them twice within the same cycle, your period tends to be delayed; the breast tenderness is a consequence of the medication. Emergency contraception should be reserved for only a couple of times a year for the real emergencies. If you do not see a normal period even after 10-14 days after you are due, please get expert help. Take care.