Help with BBT chart

Brie

Mommas, I need help understanding why my bbt is always so low and irregular.

This cycle I completed ovulation study at my RE’s office so I know I ovulated on 06/22. Also completed follicular phase blood work ( Day 3), hsg, cm analysis (post coital) etc. Everything came back normal.

So I never got an answer as to why I didn’t get pregnant after trying for 16 months with 1 early miscarriage.