What Does Irregular Periods And Brown Spotting Indicate?

I am 45 and have been later and later every month with my cycle. In December I should of started on the 5th of the month but didn't start till the 23rd. It has been very light but this is January 3rd and I am still spotting from brown to bright red at times. It is just enough to have a light pad on. Also the last couple days I have had cramps in lower adbmon.