Could it be?

As of today, I'm 6 days late for my period. I went to the doctor to have a pregnancy test done and also some other tests done. He I formed me that he believes I am pregnant however all of my test up to this point are negative. He said based on when I've had sex, I very well could be 2 weeks pregnant and my levels just are not strong enough to show up. Has anyone else had this issue that could help me shed some light? Could I be pregnant for real?