Thin, milky white discharge?

What does that kind of discharge mean? My period starts in two days, and I was thinking that might be why. I also hear that it's a sign of early pregnancy but I take my pills at the exact same time every day, so that's very unlikely I think. What other things could thin, milky white discharge mean? I dont think it had a smell, but I just noticed after I got up suddenly, I felt really wet and noticed that's what it was.