Femara and O

This is my second cycle with Femara 7.5 dosage. Last cycle, positive opk was around CD18.

Took an opk this morning CD10 and it was darker than previous days. Came home from work and randomly decided to take another and it's like a shade or two lighter than the control (and darker than this morning). I'm planning on taking another test later today, but is it possible to O early... and like a week earlier than last month?

I've used Femara in the past to conceive and don't recall any positive OPKs til about CD14 (with last 2 pregnancies with a trigger). I'm confused with the early positive opk...