Discharge before Period

What type of discharge comes before you get your period? Or if your suppose to get any at all? I know many ladies have different bodies and can experience the same symptoms or not the same at all. I’m just curious. I just went from a couple weeks of clear egg white ovulating discharge to white and a bit thick? I don’t believe I’m pregnant but I also have read that both period and pregnancy discharge can look similar. Just want to learn more about it. What’s the difference between white thick discharge and “milky” thin discharge? The consistency?