Fertile cycle changed

So my fertile window was from tuesday to Tuesday with my peak fertility day being Sunday so my husband and I had sex quite a bit this weekend to try to up or chances of concieving but this morning as I go in to track my temp and cm my fertile window has changed saying today and tomorrow are my most fertile days. Today and tomorrow I wasn't supposed to even be in my fertile window and now I'm confused. Why would it have changed? And why do abruptly?