Okey dokey.....

EWCM will stretch further than semen, which will break before stretching too far.

EWCM will clump if you put it in water, semen will dissolve.

Semen has *that smell* about it, EWCM doesn't.

Otherwise, you can check your cervix position as well as CM to help. You're after a high, soft, open cervix for ovulation. I found the best time to check CM was of an evening before bed, that way it was the furthest time since the last BD session, so there was less chance of confusion.