My cycle just changed from 31 days to 25 days, should I be worried?

Allie • TTC #1 for two years. 3 IUI`s. Miracles take time.
I'm 34 years old and have always had a 'normal' cycle.  A couple months ago my cycle changed from 28 days to 31 days, now this month it came on day 25.  Should I be worried?