AF is here but bbt still high?

AF arrived on Monday. My bbt have no signs of AF arriving though as it rose that morning. It has been confirmed that I had a chemical pregnancy after multiple positives became fainter and then negative, then AF arrived. It's been 4 days now (I'm cd4) and my temp still hasn't dropped below my coverline .. What's going on? My coverline is the fourth point in, that was my ovulation day- ​