Letrozole struggles

This is my second round of letrozole. The first round I used opk and never got a positive but through blood work my doctor determined I did in fact ovulate. 🤷🏼‍♀️ The second round I’ve tested everyday since day 9 and have not gotten a positive opk! I was wondering if anyone else had the same issue? Also tips on cervix position or other ways to help determine ovulation!!!