Plan B after effect

Carli

I took a plan B January 6th 3 days after ovulation and unprotected sex. Got my period January 15. I usually start 19th or the 24th of the end of each month always been regular. Now my calendar says i should’ve started the 14 and now 4 days late. Am I late because I took the plan B last month ? Because yes I did again have unprotected sex. But, have test and are negative. Just wanna know if this is because of the contraceptive. Thank u !