Once you reach some level of mindfulness, you start to notice that your breath is very seldom there. There are all kinds of distractions that your attention is moving to. You may not notice it and 'think' that you are watching the breath, while in the center of your attention is eg. an internal monologue or concept of the breath or mental image of the breath (how you imagine it).
> The entire point of concentrating on your breathing is that your breathing is always there and is boring!
Here you go. If there's boredom, there's no breath. If your attention is on the breath there's no boredom. Boredom is a specific mental object (state and story) and it's a distraction from the breath. 'Breath' is a concept and looking at a concept is boring indeed. If you look at the actual breath, however, you see something that's never the same, constantly changing stream of sensations, reality behind the concepts. It's always amazing, it's more interesting than anything you can ever see in ordinary closed, story-driven state of mind.