Letrozole 5mg

I took 2.5 mg the last two cycles, got a positive OPK my first cycle but did not ovulate my second. I am now moving up to 5mg this next cycle, has anyone not ovulated on 2.5 but ended up pregnant with 5? My doctor told me, it’s classic PCOS for me not to necessarily ovulate on 2.5, although I do know some women do.