Diets don't work. Cut your carbohydrates, no sugar, no junk foods, easy on fried foods.....just eat healthy which is not a diet.
I don't know what your diet consists of, so you could easily be low on iron which would make you anemic causing tiredness and adding to stress.
Go for 20 minute brisk walks 2x daily, morning and evening after your evening meal.
It's not so much the amount you eat, but rather what you eat >3