I was informed last cycle when I asked that you get EWCM for 1-4 days and you Ov on either the last day of EWCM or the day after. Then I checked it out on some fertility sites and they seemed to agree. Though I was stressing about having a 20-day luteal cycle at the time, so was happy to bring it back to 16 only for it to go to 20 again before AF arrived! Luckily I have a very sensible husband who just goes on cycle length rather than luteal phase length so didn't waste time testing.

Apparently sperm can live for up to 3 days in EWCM so that's why you get it before you ov, so the spermies can lie in wait for the little egg to come past and be ambushed. Oh, what a cute image! Little spermies with their little spears, waiting for an egg to trundle past!