1 week late bfn blood test

1 week late when I was 4 days late I got a blood test done and it came back negative with a number of < 3. I have no symptoms other than heartburn but before this the only time I’ve ever experienced heartburn was with my first pregnancy 6 years ago. I’ve also never been more than a day late. I don’t talk to the doctor about what to do next until Wednesday. Has anyone gotten a false negative blood test when 4 days late or sooner?