OPKs and Medication

Hi everyone!

I currently started on Letrozole, this is my second cycle, and ive recently noticed that my old OPKs weren't picking up my ovulation. Went to have blood work and was confirmed that yes I did in fact ovulate. So I bought brand new Clear blue Digital ovulation tests. Glow said i was suppose to ovulate today buy I got a negative on the test. Has anyone done Letrozole and not have their ovulation show up on OPKs? I hate that I'm missing out on the opportunity to increase my chances. I'm having sex every other day to almost everyday per my doctor and I didn't end up pregnant last month and I'm not feeling very confident about this month.