Lick the back of your hand and then SMELL your hand. If it smells you know you have bad breath. Now of course don't do this right after you have brushed your teeth or used mouthwash. That doesn't count. Do it later in the day.
Using breath fresheners won't work to take care of it - go to your dentist and see what the root of the cause is. It can be anything from the foods you eat to rotten teeth.