my prediction dates have changed

Mia

Hi all, I've been using this app for month now, and I've followed the prediction dates. I was supposed to get my period on the 16th and I didn't nor did I get my periods on the 17th. Here I was getting excited thinking could this be the month?!?!?! then today I have very light pink spotting. .... so I came onto the app to log my updates and noticed everything had changed??? any advice ??