Did I wait long enough before taking a pregnancy test?

Had sex on February 29 (with a condom that didn't fall off or split it anything). It's been 18 days and now I'm five days late for my period. I took two pregnancy tests today and they both said I'm not pregnant. One was a regular test and the other was an "early result test". Maybe it's just stress, I don't know, it's just that I've always been pretty regular.