Letrozol but flashing smiley only

Hey gals, first post, I’m confused and frustrated. Deal is, 9months TTC I’m 33, been pregnant with my husband 5 years ago (accidentally) but miscarried. Now trying on purpose, and since stopping the pill in October I have had irregular cycles (between 30-36 days) and my MD prescribed Letrozol. First cycle this month of letrozol - took the 5mg days 2-6 as my nurse directed. Have seen one positive ovulation test back in feb but since then been using digital clear blue 4 day OPKs and only seeing a flashing smiley (will be the death of me - that flashing smiley). Today, CD15 tested in the am got the old flasher again, ran out of tests so bought another digital clear blue and tested again, got an empty circle. WTF! Still dtd every two day’s but am I the only one with this issue ? Likely not but looking for some opinions. Thanks so much for any thoughts on this