I also agree that 5'6" and 145 pounds is normal weight. The problem with the estrogen level change (that starts usually age 30 something then proceeds gradually as we get older) it is disheartening to suddenly realize that your abs do not respond to exercise and diet the way they did when we were younger. Perimenopause is a hard adjustment to a new shape. Since estrogen is stored in fat, some doctors will tell you that the new waistline/tummy is just your body's way of storing estrogen as the production of the hormone declines.
(Sucks, doesn't it?) I've been told to just get used to the idea that my body will never be like it was when I was 21 no matter how much exercise I do.