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Since most hormonal contraceptives start giving you effective protection after 2-3 weeks of regular use, you are recommended to use additional protection if you are having intercourse during the first few weeks of getting started on hormonal contraceptive. If during your sexual contact pre-cum or semen has come in contact with vagina, chances of pregnancy are possible. Wait and watch for your next periods/withdrawal bleeding. Visit your doctor/gynecologist for further evaluation and assistance.
Take care.