Please Help

I am currently 13 days late.. I've taken a hand full of at home tests all coming back negative... got a blood test done and the results where negative as well... Dr. said that even blood tests can give a false negative if the hormones arent at a certain level... I did some research for myself and found a few articles saying that a woman took at home tests with negative results. She got blood test done a week later and same thing... A week later she was still missing her period so she got another blood test done and it came back positive... Has this happened to any of you? I'm never late and if i am it's only ever been for 2-3 days...