BBT help

Briana • Boy Girl Twins Born July 2018 at 32 Weeks after TTC since June 2015. MFI and APA syndrome. Had 4 IUIs and IVF fresh transfer prior to FET (2 early miscarriages from IUI and fresh transfer)
My bbt has been up and down the past few days which isn't normal. I ovulated CD 12 and I'm currently 10 dpi.  AF is due Wednesday or Thursday. Has anyone else's bbt done this before and if so did you get a BFP or BFN?
I know it shows my bbt isn't being taken at the same time since CD 16 but my work schedule changed so I had to move it an hour earlier but all days since CD 16 have been taken at the same time before getting out of bed so I know it's not an issue with time.