I suppose your body is not really asleep - at least not in the sense that required for OBEing. To get asleep you have to get through at least one, brief moment of unconsciousness. It is required for your body to paralyse itself in its own secret way.
If you could keep your consciousness intact through that period you would feel noises and/or body vibrations. In this case you could easily recognise your state and start efforts to separation. However, if you miss that moment you could think that you are still awake.
Thus, I suggest you to check your state regularly, and especially in that moments when you found yourself awakened from a hypnagog attack or brief unconsciousness. You could check your state by refocusing your body awareness into a point just above the top of your head and move that point slowly upward along the axis of your body. This would gently assist you into paralysis provided that you are already close to it.
If you could keep your consciousness intact through that period you would feel noises and/or body vibrations. In this case you could easily recognise your state and start efforts to separation. However, if you miss that moment you could think that you are still awake.
Thus, I suggest you to check your state regularly, and especially in that moments when you found yourself awakened from a hypnagog attack or brief unconsciousness. You could check your state by refocusing your body awareness into a point just above the top of your head and move that point slowly upward along the axis of your body. This would gently assist you into paralysis provided that you are already close to it.