OPK or not

Last month I ovulated on my own (confirmed with bloodwork and ultrasound) and had a period that started December 3rd. On day 3 of my cycle my RE had me start femara and yesterday was my last day. My RE told me not to even bother with doing OPKs and just to have sex day 10-20 every other day. He is not monitoring my cycles on femara and just said to try 3 cycles and if it doesn’t work, move on from there. Should I still do OPKs anyway and if so, what day should I start? My cycles have been irregular and I went 6 months with no period until I started taking Metformin after being diagnosed with PCOS and this was my second period since starting that.