The CM or Semen debate

The CM or Semen question!
 
So, today is the first day of my fertile window (Tues) and I am expected to O on Sat. We had sex last night and this morning when I woke up and went pee, a huge glob of EW CM was dangling there (sorry) is this old semen or fertile CM? Gah! I've heard semen turns very watery after sex. 
Thoughts? Experiences? 
Thanks!