What Causes Delayed Periods After Taking Take Action Pill?

Hi. It was the day after my period ended (April 9), and we didn t have penetrative sex, but I freaked out because I felt some semen on the inside of my upper thigh. To be 100% sure that I wouldn t get pregnant, I took a Take Action pill within 24 hours.Six days later (April 15), I started bleeding lightly, which lasted 3 days, not as heavy as a regular period. I understand that light bleeding after taking an EC is common. I didn t worry too much about that. My periods are usually 28-31 days apart. Counting from the day my last real period started on April 3rd, I should have gotten my period around May 3. It s been three days, no period. I am getting sick with worry, because I m not sure if I should count thirty days from April 3rd, or from April 15th, to determine when I should be getting my period this month. It would be a great relief if I knew that I should expect my period thirty days from April 15th, i.e. around May 14th. I d stop stressing this much. When (if at all) should I take a pregnancy test?