Confused

Tiffany • Live*Laugh*Love
I took 3 digital pregnancy test, 2 different brands all came back positive, however, when I went to look at the test today the positives disappeared from all of them. One was a Clear blue test that states if you get a positive it will stay for up to 6 months. Is this common? Now I'm beginning to think I'm actually not pregnant and I've already got my husband excited =\