I have practiced anapanasati for a while and encountered some difficulties. I can easily find my breath in front of nostril. Then I started to pay attention to the in-and-out of the breath continuously. But after a while, pain raised in my chest around heart. As I tried to focus more on the breath, the pain increased. In addition, if I suddenly stopped paying attention to the breath, I found my neck and shoulder very rigid and uncomfortable. I also felt exhausted after the meditation.
I’m wondering if I focus too much. Before I know anapanasati, I used to practice simple meditation like just relaxing and checking any thoughts if they arise. I felt much better by not paying attention to any object.
So my question is: what is a good “attention” to breath? Thanks!