Seeing how body reacts to going off BC

I’ve been on birth control for over a decade now and typically skipped the placebo pills so I have no idea what my cycle is like. Due to an issue with my insurance plan I ended up with no BC in the mail for me this month. Planning on TTC starting in June and wanted to take this couple of weeks with no back to see how my body reacts fertility wise and I am so confused.

I’ve been taking BBT for 4 days and it’s been all over the place. I took a clear blue digital ovulation test the first morning and had low fertility (expected) but this morning I took one and had high fertility - wasn’t expecting that! What were your experiences with going off bc?