3 positive FR HPT but negative test at pregnancy center

So I had three positive pregnancy test at home on the second day of my missed period. But then went today to get a confirmation test at the pregnancy center and they said it was negative. Yesterday would have been 5 days late and I’m never late. I started spotting yesterday and it’s turned into brownish spotting. What could this mean?? Should I wait another week to get another test done if aunt flow doesn’t show? A lot of people have told me that spotting is normal. According to my last aunt flow I would be about four weeks... but I have no idea what’s going on.