Positive but sitting the test on its side?

Janet
I took a test this morning (3 days before period) and set down the test for the 3 minute window. When I went to go get it I realized I laid it on its side but I had a strong double positive line. 
I then took a test this afternoon and it came out negative. 
Do you think laying it on its side caused a false positive? Or is it because I have less hormones in the afternoon?  I still have a few days before period but no idea what to think now!