6 positive tests and one negative digital

E.
So my period is three days late. On the day my period was due, I took 5 pregnancy tests (2 of those were digital) and they all said I was pregnant. Yesterday I took a regular blue line test and it was positive. Today I took a clear blue digital test (same one I took two days ago) and it said I was NOT pregnant, even though I took that same test two days ago and it said I was. What is going on???