Femara and OPKs

I’m on my 3rd cycle of femara and I’m having issues with opks. My first cycle I was on 2.5 mg CD3-7 and had my first positive opks (stick and digital). Last month and this month I have taken 5 mg. I started opk testing CD 10 and got a positive stick test on that day but negative digital. I never got another positive test from either last month but when I had my CD 21 blood work done my level was 17 so they said I did ovulate. Has anyone else had this issue and might be able to give me some advice?