Is it possible to be farther along than you think? When I first took my pregnancy test last…

Is it possible to be farther along than you think? When I first took my pregnancy test last Saturday.. As soon as the pee moved across the window it came out positive. I took another one today, and the line was super dark. That's a good sign isn't it? I've read that it means your HCG levels are higher which ha a good sign.