still worried

i still have not gotten my period. i didn't have vaginal or anal sex. im still a virgin but i did give my bf oral sex and later that night (an hour later) had phone sex with him. i have asked a whole bunch of people if i could get pregnant. i was told no, however my period has yet to come. my last period started may 14th. i took two pregnancy test and both came back negative after my missed period date. when stressed i skip periods, should i be concerned?