What Causes Late Period With Unprotected Sex?

Hello doctor, My period was suppose to come on June 2nd but it was late, I haven t been sexually active since December of 2013, however on June 6th I had unprotected sex where my partner used the pull out technique and didn t cum anywhere near my vagina however I m worried as my period is roughly 6 days late now. Should I be really worried? And why is my period late it s never been late before. Thanks a million