okay im on yasmin birth control, and i take it pretty regularly, although sometimes im an hour or 2 late, but i take it every day..we also use a condom except not the entire time, we usually put it on before hes about to ejac...so I took the plan b pill 2 days ago because the condom slipped off after he came and i was on the reminder(inactive pills) and i didnt know if i was still protected by my birth control, so i took the plan b pill..i was supposed to start my period today (usually in the afternoon) and it hasnt arrived..i really dont have any cramping or anything and im freaking out..could it be late because the plan b pill i took 2 days ago? i took a preg test (first response) and it was negative...should i be worried??

please help, and only give serious answers, im already stressed enough :-(