OPK test kits

My doctor told me I’m not ovulating. My progesterone was 1.2 the day after I was suppose to ovulate. There’s no anatomical problems per an ultrasound. Next step is an HSG test. ($600+). So the doc suggested opk test kits to see when I *should* ovulate. How long did it take you to get pregnant using them? Did anyone else have this problem?