What Causes Delay In Periods And Light Spotting?

i hd unprotected sex with ma girlfriend on 3rd feb at around 2:00 pm n she took ipill on 6th feb at 1:00 pm ,we again hc physical on 6th n she had ipill same day , her periods are due on 5th n she hv got it yet , on 22nd hd bleeding for half n hour n spotting then onward no sign 4 period ..... are there chances on pregnancy.