I'm 17 years old. I had unprotected sex with my boyfriend last month (January) on the 29th (Thursday). I have a 8-12 day. My period was expected on the 13th of this month (February, Friday). It's been two days and I still haven't got my periods and I tried two testes but both showed negative. How does the Saheli work? Should it be taken on the expected day of the period, even though I've missed? Or should it be taken from the day I actually start bleeding. No period, but still negative? What does that mean?