You know when you’re counting your breaths in the Mindfulness of Breathing, and you manage to keep the numbers going continually and follow the sensations of the breathing, but you also have a continuous stream of thoughts going on? You probably get very annoyed by this. But you shouldn’t.
The continuity of awareness that accompanies the counting is valuable, and it’s part of what we call “access concentration,” which is where you’re on the verge of a “flow state” in meditation where everything becomes much easier and distractions fade away. So this “multitasking” stage (noticing the breathing, counting, thinking) is actually a helpful thing. We just need to take it a step further.
What you’re lacking in that access concentration state, and what you need to bring about, is just a bit more calmness. I’d suggest trying to pay attention to the breathing more fully. Notice what it is that you’re actually paying attention to when you’re “noticing the breathing.” And then notice what sensations connected with the breathing you’re not paying attention to. Start adding them in, to the point where it’s becoming a slight “stretch” to notice so much, but not where you feel actually stressed. That “stretch” will bring your mind to a point of quietness. So you’ll have the continuity you’ve already established, and you’ll have calmness to go along with it.
I just want to say one more thing, which is although I’ve mentioned the potential for “states” arising, we just need to stay with our moment-to-moment experience and engage and work with it, and not grasp after the arising of any kind of state in meditation. Grasping after happiness in meditation is the best way to make sure that you achieve unhappiness.