Okay not to be harsh but I agree with the previous person to a certain extent. In your post you answered your own question.
The reason why you smell so bad is because of what you eat. Your body is telling you that it has had enough and that it will not digest or attempt to take what little enzymes and nutrients you are providing it. In other words your digestive system has slowed to a grinding halt. Fast food is packed into your colon and your system and it just rots there without moving thus causing the smell. Also possibly with the food breaking down in your colon you could be a breeding ground for a Tapeworm and/or parasites.
You really want to smell better then you need to learn how to eat to live and not live to eat. Its very hard and took me almost a year to admit it but you dont have to go hardcore cold turkey mix fruits and veggie until its all fruits and veggies and some grains (when your system is ready). I did The Master Cleanse and then went vegan. Your body needs to purge itself of all the chemicals and old food in your system and then needs to be restored with proper vitamins and enzymes that you can only obtain from fruits and veggies. Its a long hard journey but you will appreciate your body more if you do.
You want us to help you then you need to help yourself.Seriously, though stop with the dairy, fast food and other stuff because its going to get way worse.