Ovulation dip WTF


So my charts usually look normal (see last 3 month overlay). But this month instead of having a BBT spike I’ve had a massive dip!!! I’ve also had less of my usual ovulation pains (sore nipples and pelvis.... although still slightly there). WTF is going on? I always ovulate on day 20 (last 12 months or so) but that was yesterday and still no spike 😦