Letrozole/OPK Question

My Reproductive Endocrinologist put me on Letrozole this month due to my late ovulation/long cycles (O around CD21, cycle length around 35 days). But, I do consistently ovulate and have a regular period every month. I’m only on CD8 (just finished the letrozole) and I know this isnt positive yet but its pretty dark for only CD8! For those who have taken Letrozole, did you ovulate much earlier than you did before?? I feel like I’m gonna surge in a few days which is so early for me 😱