Emergency contraceptive does actually throw off your cycle. They say it can be about 5-7 days after taking EC that you should bleed. I'm told that is the indication it has worked. Continue using your BC how you normally would, it might take a month or 2 in order for your cycle to get put back on track, even on BC. I had a friend a few years ago who had to take EC and her cycle was off for a few months. Ususally it takes about 2 weeks from the time of sex to test for pregnancy, you have waited a month. You should be fine. You could test again if you wanted, but I think it's just the EC throwing off your cycle.