What Could Cause Menstrual Irregularity?

I am due a smear test and told the time to have it done is between 8-10 days after first day of bleeding. But last month my period stopped (I am 42 and know I am not pregnant) I was wondering when I should go for smear test. Should I wait until next month to see if period happens again.
In addition my stomach area is really really itchy - I'm not sure if it is related or coincidence.