As far as I can make out Your required calories per day drops by around 200 a day
If you are also not doing any weight bearing exercise then you lose muscle quickly at this age. Since muscle takes more calories to maintain then fat, that's another 200 calories a day. And for the same weight, a person with more muscle looks thinner.
That's 400 calories a day less than you used to eat ( average height etc) so to stay a steady weight , you are needing to eat what you used to consider a diet.
Where weight sits also moves towards the tummy, that's just tough really. Need less weight.
Also menopause can make you a bit weary. So you become gradually less active, watching more tv and doing less pottering. And that means fewer calories needed again. I think this one is particularly nasty, because if you have poor sleep it's really really hard to keep active, and other changes such as ch8ldren growing up mean you have less need to be generally active
So the usual , Eat less, exercise more , especially weights. It is hard, but if you catch the dreaded weight gain early , like you have, I think it will work
Recently gone back to pump myself. I know it's good for me . Just start again with small weights