Hi, Dawn!
I'm 51 and my periods started fluctuating in cycle time a couple of years ago. This last year all heck has broken loose!

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Cycles from 15 - 75 days. Sometimes with the usual warning signs (sore breasts,, spotting, etc.) and sometimes a complete surprise (thank goodness I work at home!). Some months are so light it's hardly a period at all and some months it's the heaviest it's ever been. Some months last 3 days and some months 7 days.
I'm not on oral HRT but recently started vaginal estrogen for VA.
What is helping me is recording all my symptoms (physical and emotional) on my Garmin watch. The Garmin app then charts all the info. I'm only a few months into doing this but can already see patterns emerging.