I know when I get chilled or cold - I tend to clamp my arms to my sides and hunch my shoulders/neck against the cold.

this tightens up the armpits/ pec minor areas.
maybe making that whole area get tight and then clamps down on the structures there - nerves, muscles and lymph nodes.

I wonder if you or someone gently tries a lymph massage for those places if it would relieve some of it or not?

lymph info & technique
they updated the look of their site- it seems to have more detailed info now too -on the muscles and everything - {from our stickys}

http://deeptissue.com/articles/lymphatic_article.html
http://deeptissue.com/articles/lymph_technieque.html
http://deeptissue.com/learn/learn.htm