I Spotted A Drop Or Two On April 4th My

i spotted a drop or two on april 4th my last period ended right on the 19th of march I took a few dollar test to find out if I'm pregnant the frist there was nothing the others said negative 4 days ago I went for a blood test that came back also negative. I have had 3 live briths and I had one miss carriage my last child was just born last year aug 7 2014. I believe and feel that I am pregnant but the test show differently and this has never happened to me before. please some help what it might be or is it to early to tell.