Letrozole first round

Hi! I was on clomid and no success for baby #2. Dr switched me to letrozole to start taking today, day 3-7. Any success after the first round? Also, opk help!!! I use the clear blue digital. Would you start to try once you get the flashing smiley or before? My plan was to start day 8,10,12,14,15,16 or once I get a solid smiley face to do 3 days in a row. Help! So confused !!