Gaining weight is normal with age. Lack of exercise, but mostly eating more will make you gain weight. It's hard to lose weight when a person eats more than he should. You know that if you would eat less you would lose weight, so the problem is not there. You want to gain controle and eat less, but probably you can't. Something inside of you is telling you to eat alot. Eating is also a habit. I gained 10 lbs in the last 5 years. It's maybe not much, but still I was wondering why? I've been eating more, that's why. Now why have I been eating more? That's what I'm asking myself.
In my case, these 10 additional pounds were good for me, because I was slim, and now I'm normal for my height.
The bottom line is you have to eat less to lose weight. It's simple, but hard to do. I think that a person should not change what he eats, but the amount of what he eats. Personally I noticed that eating desserts made me gain weight. Try skipping desserts for a couple of weeks, and you will lose weight, it's guaranteed.
Depression, like you say, makes you eat more. Try not eating as much for only 2 or 3 days, and when you see that you lost 3 or 4 pounds, it will make you feel better. You will be less depressed and more proud of yourself. A pattern might set in, and if you keep on, and then, you're on a winning streak...