Help?? When did I ovulate?

I usually ovulate CD15.. this month I was away without my tests so didn’t start testing till CD 13. I expected it to rise the next day, as it has every other month but it dropped. I assumed I ovulated early, even though I didn’t notice any fertile CM, and missed the window to test.

Flash forward to now, I’m expecting my period in 3 days, and suddenly I have fertile CM. I took two OPKs today and the number is rising.

I’m so confused. I have my “period is coming” symptoms.

I’ve taken a pregnancy test and it’s negative.

Why did I get a high number on CD 13, and why is it rising now..??