Femara cause early ovulation or false positive on opk?

This is my first month taking Femara and doing IUI. Usually my cycle is relatively predictable, meaning ovulation happens around cycle day 13-18 and menstruation happens 14-15 days after. This month I took the Femara from cycle day 3 through cycle day 7, then on cycle day 9 took my first ovulation test. My digital opk test said ovulation was high but not peak and the fertility office wanted a call at peak ovulation. On cycle day 10 the opk test was low and has been low for each day from 10-13. This is my first time doing any of the infertility treatment and my first time taking Femara. I’m a little worried that I missed my ovulation. Does anyone know if Femara can cause false positive opk or early ovulation?