Breath and our thinking are connected. Pressure occurs within our perception. It is created by ourselves. It is related to our understanding of life. Our understanding of life is related to our thoughts and therefore the flow of our breath.
If you are choking, this means the flow of energy is constricted as a result of your understanding. You must therefore evolve your understanding.
Our understanding evolves by living with awareness. We can learn what awareness is by practicing meditation.
You can study this article about meditation and start practicing. Practicing according to the instructions will teach you to live in awareness, this in turn will evolve your understanding and you will learn to deal with pressures, even learn how pressure is being created in your experience and how not to create it.
This article also contains extensive information that can benefit you in evolving your understanding.