21 day cycle while ttc

In the 4 years I've been tracking I've never had a cycle this short. I'm usually a solid 30-31 with random 28-38 here and there. The last few months I'm consistently 31 days. I thought I had just ovulated a few days ago and had roughly 10 more days til AF but to my surprise HERE SHE IS!

I have not changed diets, weight, lifestyle, or been stressed. Curious if anyones experienced this or if I should be concerned? We've been TTC over 2 years and really thought we caught the egg this month.