Help trying to pinpoint ovulation

Allyson

We are doing the Shettles method and trying for a boy. He says do time intercourses within 12-24 hours of ovulation and ovulation should occur right at or after the dip, but before the spike in temp. Do you think that’s been DPO day 16 april-May) and DPO day 12 (May-June)? Trying to pinpoint it for this month