You really do not have to notice the breath. Look directly into Lord Buddha's words in Anapanasathi Sutta. You have to establish your awareness at the center of the upper lip and you should be aware whether you are breathing in or out, long or short, etc. If you do feel any sensations at the center of the upper lip notice it also. If you cannot track whether you are breathing in out out, long or short few intentional slightly deep breaths are OK but you should stop making intentional breathing once you get to this.
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