I have never had this happen before so I'm not sure what to make of it. Any help is greatly appreciated!!

I had a positive OPK on CD 15. I usually continue to check my LH levels until they turn negative again {I typically have positive OPK for 2-3 days} but I woke up on CD 16 with a huge temp rise as if I had already ovulated. Since I figured I ovulated, there was no need to check it again to see if my LH was still up. When my temps dropped back down on CD 17 I assumed it was because I didn't have a great night's sleep or maybe I slept with my mouth open or some weird fluke. But then this morning my temp is STILL back down and I slept fine through the night. Any insights on what this means??

(Note that I know we did not do a good job of BDing this month but we needed a breather from 6 months straight of 'intercourse on demand' and we just had sex when we actually wanted to... Which meant not a lot this month obviously ha. And the meds I marked are for Vitex.)