How to handle torpor?

I've been practicing concentration for a while, trying to reach access concentrataion. In the beginning of my practice my mind was very noisy (as I guess anyone else), after a while I began to calm down and thoughts began to slow down enough for me to see the way to concentration. I experienced how tracking the breath and taking in all the texture really changes the state of my consciousness and feels like plunging to a deep water. It seems that this is a window to a wide world I really want to explore. In recent sittings I've been finding myself calming down very much to the point of not focusing on anything at all. No thoughts, no breath. I guess there's still thoughts and activity but my mind is not in tune to any of them in particular. While this can fell quite good, I think its retarding my practice. I notice that its now hard to track the breath in the same way, its like the mind is being lazy and wants to slip into the comfort of being dull. There's no texture to the breath and it now feels more distant. What can I do to overcome this state of torpor and inject some clarity into the practice?