I have this cramp which is on my upper left chest, right below the neck and adjoining collar bone. It's been there for the past month or so and I feel a pain only when I stretch my left arm above head, or when I am taking my shirt off, or when I come of from a face down lying position with pressure on my left arm. It is weird because this has lasted so long. As per me and my body, it shouldn't have lasted that long. Now I am not sure what it is and what can I do about it. Please suggest what should I do? I thank you all in advance. Best Regards