Aarh- cheer up! Chins up OP!!!
I think you have to accept that your body changes- mainly due to loss of muscle mass and hormones.
Nearly everyone in mid life finds that they will put weight on if they eat the same as they always did. I do! I am not overweight but my waist is almost at the stage where it is a risk factor, and I am currently trying to lose another 3 lbs. I did have a waist of 24 in my 20s. Now it is 29!
I will never have a 24 inch waist again but 26-27 is my goal.
You need to do 2 types of exercise- cardio and resisitance.
Resistance is working your muscles against gravity to build muscle mass.
Muscles burn more energy even when you are standing still - so more muscle means you can eat perhaps what you used to and still stay trim. With muscle wastage, you will have to reduce your calories even more.
Try lifting dumb bells, or using a machine at the gym, and doing squats and lunges to strengthen your legs and back.
Also, high intensity work outs of a few minutes are better than longer periods of more moderate exercise- which is why some people walk then sprint, walk then sprint, for a few hundred metres.
Don't give up- sounds as if you just have to tweak things a bit.