Hello, I would be happy to help you with your question.
First of all, you probably ovulated on about 2/18, well before this episode of unprotected intercourse
(assuming you had regular cycles). In addition, even if ovulation was off, the emergency contraception
further reduced your chances of pregnany (but it is not 100%) effective. My guess is that you are NOT pregnant, and these pills have had the effect of delaying your next cycle. This is a common effect. It is of slight concern that it did not induce a withdrawl bleed, though. You need to:
1. Check a pregnancy
2. Repeat the pregnancy test in one and two weeks from now
3. Always be prepared with condoms and consider some other form of birth control moving forward
I hope that this helps and good luck!