Ovulation on Letrozole

Hello, I finished my first dose of Letrozole this cycle. I’m on CD13 and went for my ultrasound today. They said my left ovary has two dominant follicles one being at 21mm. She said I either already ovulated or am about to. I was just wondering if anyone else has experience this around this time and when did you ovulate? I took a opk the last few days and they’ve all been negative. Has anyone gotten pregnant on Letrozole 2.5mg three times a day for cycle days 3-7???