Ovulation

2nd cycle of femara. First cycle was 2.5mg didn’t ovulate till around cycle day 28...used the regular clear blue digital...Had the smiley for about 4 days. This month my dose was upped to 5mg. I switched over to the clearblue advance. I’m currently cd 15 and this is my second day of the flashing smiley. How long does the flashing last? When should I expect to ovulate?