This Weekend, I Took Six Home Pregnancy Tests (3 Digital)

This weekend, I took six home pregnancy tests (3 digital) that all said positive. They were early result tests, as I was testing two days before my missed period. The last test I took was Monday morning. On Tuesday, I went to the doctor and got a negative urine test, though they did draw blood and I am waiting the results. I still have not gotten my period, so I am wondering what the cause could be.