I've been taking the same dose of letrozole on the same cycle days for 6 months. The past 5 months I have ovulated while on it- proven by day 21 progesterone tests- except I forgot to go in this month so I'm not sure if it worked this cycle. But it worked for 5 cycles in a row. I usually get AF on cd 31-33 and it's now cd 35 and no AF. I took a test yesterday afternoon and it was a bfn. Is it possible that the letrozole stopped helping all of a sudden? Is it possible it was too soon to test? Please give thoughts, advice, words of encouragement! Thank you!