You must find out at once if there is a physical reason for your tiredness. Go to a doctor and get a check-up. A low HB-count, for example, can cause tiredness. Another cause of tiredness is overconsumption of coffee which gives only a short stimulating effect followed by even greater tiredness. Dropping the habit of drinking coffee may temporarily make you even more tired, but when you have managed it you will feel better and less tired. If you look after your health with wholesome food and exercise you won't feel so tired anymore. More about medical causes of feeling tired.
It is obvious that you use eating in order to relax after work and on weekends you use it instead of company and pleasant occupations. You need to find other sources of happiness will give your life meaning without filling your body with unnecessary calories.
Here are some examples of things you can consider doing at weekends.
When you come home from work you should try to find something which can replace eating junk food. If you are hungry, eat a good meal. If you feel stressed, a relaxing tape or a hot bath can help. Perhaps you should go to bed and sleep. Those who stay up when they are tired often eat more in order to keep awake.
When I read your letter I had a feeling that your eating is a way of escaping from something you find difficult to manage. Your life would be happier in the long run if you tackle problems instead of running away from them with the help of junk food. If you have difficulty identifying and solving these problems, you might need the help of a psychotherapist.