Bbt dropping but still pregnant?

Kris
Has anyone had their bbt drop but still been pregnant? AF hasn't come yet (according to ovia she was due yesterday...according to glow she's due Thursday). Had a drop at 8dpo and then spike up at 9 dpo. At 13 dpo now and temp dropped like .5...haven't lost hope yet but I'm hoping some of you have had that happen but still ended up pregnant..