Hi I Had Unprotected Sex With My Boyfriend & Took

Hi I had unprotected sex with my boyfriend & took plan b, even though we're both 90% sure that he pulled out in time. After that we've been having unprotected sex atleast twice a week since the first week of Feb. but we're 100% sure he doesn't cum in me. But I've missed my period for Feburary & my March period was due today, and I haven't gotten it yet either. Is this normal?