stinkydoug
Most likely you do not smell bad at all. Look at all the evidence. You have all the people that know you telling you that you don't smell and not one ever told you that you smell. People cough and sneeze all the time and there's no reason to believe that it's because of you.
My advice to you, go on with your life on the assumption that you don't smell. If you ever encounter conclusive evidence of someone thinking that you smell, like a stranger pointing a finger at you and saying you stink, then consider looking for help.
If you want to find out how people react when you really stink, buy some raw fish, let it rot for a week at room temperature, then strap it to your body under the t-shirt and go into a crowded mall or a bus.