Welcome to the group and I'm also post menopausal (hit menopause before I was 30, being young and being in it that means I have another 50 plus years a head of me to live with it).
As to how it can happen, simple some women just do not have as many eggs as others and once you run your course you go into menopause, for other's its more hormonal and you might appear to be in menopause but really aren't (bit more complicated to figure out or so I'm told).
You are also not doomed to be over weight thanks to the PCOS and menopause, it just means you have to work that much harder to find what will work for you. I've been working on a form of the GI plan though the Canadian Diabetic Association (since I'm also diabetic) since the start of the year I'm down two pounds so far so good, since last year all I lost was a single pound.
Nyxks Musings nyxstium.info twitter.com/nyxks/
Cals Burned for 6 years = 2,359,000
6 years Deficit Total = 1,729,800
Should have lost: 250 to 495 pounds
Actual loss = 139 lbs and 50 inches from core
| Pounds lost: 51.1