I do not pretend to have all the answer and only share what I have observed and learned in my old age.
I hardly eat at all.
It isn't always eating habits that cause weight gain Lind.
The first thing (in my opinion) if you are being truthful by saying you don't eat much and are still gaining weight is to have your thyroid checked.
Your thyroid can really throw your metabolism off.
I have found the same with sleep.
If you are not getting the right kind of sleep it can cause weight gain.
Did you start taking a prescription drug that could have triggered your gain ?
Did you start a job where you don't get any exercise like you use to ?
There are so many variables and medical doctors just don't have the time to deal with overweight people because they really have not been trained in nutrition.
My advice if you are serious about correcting this problem is to find yourself a good Homeopathic doctor that can help you figure out why you have had this weight gain.
I was always very thin and tiny until about 10 years
Then obviously there has been a major change that has occurred in your metabolism that was not your fault for eating to much or the wrong foods.
Remember though as we get older our metabolism slows down so we don't need as much food.
Cardio is another contributing factor.
The first ten minutes of the day do an exercise that gets your heart just pounding.
This puts all your organs into burn calories mode for the day.
Very simple but people are just to lazy to do it.
Remember that it took you ten years to put it on so don't expect to take it all off in ten weeks. ;-)
The most important though is DON'T GIVE UP !
Never quit trying trying.