PCOS & Letrozole

Has anyone with PCOS ever been put on Letrozole to start ovulation? I don't have a cycle at all, ever! So my OB has me taking Progesterone to start a cycle and then Letrozole to start ovulation. Then after testing and everything I have to wait until CD 42 before I can start another medication cycle (pending a negative pregnancy test). I don't know if the meds of pcos affect pregnancy tests and I don't have a normal cycle so I never really know when to take a test. I haven't met anyone who's taken Letrozole before so I've not been able to get any advice! Any information would be appreciated!