Ovulation tests and Femara

Brittney
Okay, so my doctor put me on Femara (2.5 mg 2x daily on CD 3-7) (This is my first cycle on Femara). My cycle started Jan. 4 and I'm on CD 18. I went for an ultrasound on Tuesday (Jan. 17) and I had a follicle just under 2 cm and my doctor said ovulation would take place any day now so to BD every other day, which I've been doing, but I've been taking ovulation tests and they've all been negative. Just wondering if anyone knows if Femara can have any effect on ovulation tests?