BBT - Luteal Phase question

[Anonymous]

I had a clear shift that suggested ovulation about five days ago, from temps around 97 to a 97.7. Next day it went down to 97.6, then I had two 97.4s and now today it's 96.8. I'm worried about this gradual fall--could it mean that I'm low on progesterone? I'm on a natural cycle this month, but I have had four IUIs in the past so my blood was tested on 3dpo/iui and progesterone was always ok then. however, it was never tested after that so I'm worried that I could have some type of progesterone deficiency that just doesn't show up til later in the cycle.