I don't know of any way you can change when you O.

I very rarely got EWCM but on the cycles that I noticed it I always seemed to get pregnant so for me EWCM was essential. I got a BFP on one cycle where I used 3 times the usual dosage of evening primrose oil for the week before O and then I stopped taking it. I was temping at the time so I knew when I O'd.

With this pregnancy I only saw one "glob" of EWCM - we DTD right there and then and I was pregnant. It was the only EWCM I saw during that cycle and I hadn't seen any for the previous 3 cycles where I was unsuccessful.

Try not to stress about it though, it's perfectly normal to take up to 12 months to conceive a baby.