Pregnant? or not?

Patient: I was ovulating the 24th of February. I had unprotected sex the 21st and 23rd and he ejaculated inside me both times. Then I took plan B pill the 25th. I don’t know if I took it too late. Now I am 8 days late on my period and it’s very unusual. I have cramps but don’t get my period. I took a pregnancy test 7 days after my missed period and it came out negative. Is there really a chance that I’m pregnant?