Could I be pregnant?

I had unprotected sex twice in two days (July 25-26). My partner did not ejaculate either time and I was not ovulating. Just to be safe, I took the morning-after pill Take Action the following morning (27th). My period was suppsed to start yesterday, but it hasn't. I am unsure what to blame: the pill or a pregnancy.

Yesterday, impatiently, I took a First Response pregnancy which came out negative. I plan to wait about two weeks to test again.

Should I even be worried about pregnancy considering the circumstances: No ejaculation, no ovulation, two days before my expected period and a dose of Take Action?