CM question

A few things...
1) Can you CM drastically change throughout the day? This morning I had stretchy, sticky CM and tonight it's changed to watery CM. 
2) What's the difference between watery CM and egg white CM? Is the egg white the most fertile and the watery leading up to it? The app is predicting that my ovulation window is beginning in two days! Just curious as to what the difference is in the two CM types.