You could try the slimming world diet. It doesn't consist of exercise, and you can eat as much of anything that you wish!
The way it works is that each food has a 'point' system. you can have 10 points a day, or say you have 5 points one day, you can have 15 the next.There are free foods (such as chicken) and red days and green days where the points differ. See? It's easy! Here's the site, i know it's english, but it's pretty simple to figure out
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Also, stress will also cause you to gain weight, try not to worry, or be upset! Everything will work out. Your problem may be that you simply havent found the right diet that fits you.