I was three days late when I tested, got a positive result, both test I took came back positive in less than two minutes.
Mine showed positive being one day late on my books but Dr said on her books I was 3w 6d and popped a positive. So everyone is different.. good luck girl :)
You might of took it way too early because when my period was missed and I took a test it was negative but when I took it a couple days after it was positive. Give it sometime
Take it the day of your missed period or after (that's even better). Any earlier than that and you're not as likely to test positive because your hcg levels are not high enough.