Pregnancy test question?

I know this might sound a little dumb but what does it mean if my pregnancy test lines are getting lighter? The first one I took with FMU a faint line came up and then the following day it got darker when I took it at 11pm a few days later and this pregnancy test is lighter than both and I’m using FMU? Is this a bad thing?? Any advice helps.. btw this would be my second baby but never had this problem with my first, they always kept getting darker. My appointment isn’t until Mar. 6