Does nortriptyline change the effectiveness of Birth Control? I've been on some sort of BCP for years. I recently switched to Mircette (5 months ago). I started the Nortriptyline about 6 weeks ago. Since then I've had 2 periods. The first one was very light and only lasted about 14 hours. The next one was the one that's happening now. I've never been in this much pain. No kind of pain medicine, OTC or prescription, helps. The period is very heavy and incredibly painful. Any help would be very helpful!