Question about cycle

I have been lurking for a while and I have a question.  I have TTC for a while and I am 42 years old.  Usually my cycle is 31 days like clock work.  I am on day 44 of this cycle and no period yet.  I tested last Sunday and the digit test said not pregnant.  If I am not pregnant and just missed this period, does it go back to the normal number of days i.e. I would be on day 13 of this cycle.  I am kinda confused since this has never happened to me before.

Thank you for any answers.  You gals are great!

Beth