Period is 2 days late...

I was supposed to get my period yesterday, Sunday. In the last 3 months, it has been arriving on the date expected. It is now Monday evening, and I definitely feel like I'll be getting it tomorrow. My question is, since Glow predicted my period to arrive this past Sunday, how do I change it so that my next ovulation dates will be accurate since my period is late this time?? (I took 2 pregnancy tests, both negative. Plus, I'm getting my usual day before period back pain)