Yes, both working night shifts and taking emergency contraception can absolutely cause your periods to come more frequently. Emergency contraceptive pills contain hormones that temporarily disrupt your natural cycle, often leading to irregular bleeding or shorter cycles. Additionally, night shifts can disturb your body's internal clock and sleep patterns, which also affects the hormones regulating your period. This is usually temporary. However, if this pattern of bleeding every 15 to 20 days persists for more than two or three cycles, it is a good idea to consult a healthcare provider just to ensure everything is back on track.