stop thinking...just tune into the sound of your slow breathing without actually paying attention or trying to hear it. just let it dissolve into sort of a backgrounds noise that is present when you are out on the street but not paying any attention to it. you will shortly start hearing buzzing and sense separation. it's cool to contemplate on things you feel and hear in the process but at some pint you really just need to stop analyzing all sensations and sounds and just let go.