Anyone on 3rd cycle of 7.5mg letrozole?

TTC for a little over a year now. Had 3 failed cycles of clomid then was put on letrozole because i have PCOS. My first round was 5mg but it did nothing then i did 7.5mg and grew 3 follicles for the first time and a positive opk but started taking the meds 3 days before my period and it was unsuccessful. Now im starting my 3rd round on 7.5mg on CD 3-7. I feel positive that if i started taking the meds before my period and my follicles were 16mm that now that im taking it on my 3rd cd it could grow stronger allowing a baby to come from it. What are your experiences?