late period...

Alright, so I'm 3 days late on my period and I've taken an early pregnancy test and it came back negative. My man and I made a mistake of having drunk sex a little over 2 weeks ago on my 15% fertile (ovulation) day. But again, negative test... I suppose if I don't get my period the rest of this week I'll test again next week. Anything similar happen to any of you?? I'm so confused