Feeling discouraged

Its CD 19 and still no ovulation. This cycle i took 10mg femara(letrozole) i dont understand why im not ovulating as i have ovulated on this dose in past even got pregnant with twins on it. Which i now have my 4 almost 5 year old from it.

Im just at a lose and feeling defeated.☹

This is what all my opks look like but my digital has been saying high fertility since CD 14