Missed Period after iPill. Help us out.

Hi, My girlfriend and I had a brief encounter of unprotected sex on 09 April 2017. It lasted for a couple of minutes and I did not ejaculate. We popped in an iPill within 10 hours. Her periods were due on May 1 but she has not had them yet. We have taken 4 urine pregnancy tests in the last two weeks, one with urine held for 5 hours, one with normal urine, and one with the first urine in the morning. All were negative. 1. We had sex on the 12th day of her cycle. 2. Her cycle lasts for 33-36 days. 3. She bleeds for 2-3 days, light flow. 4. She was diagnosed with PCOD a few years back and her cycles have been fairly regular. We read on the Internet that all this could be due to iPIll. What should we do, we are very stressed, please help us out.