Which breathing technique?

My breathing is quick and sehr shallow. Its not somthing I consciously force but im not sure its healthy. When riding in a group those around me start to unnerved, last week I was on a climb and a group of overweight old men I eventually overtook were worried (in french) I was about to expire on them.

Glad we have some budding neuroscientists on this thread as I think its related to an automatic nervous system response attempting to control my blood pressure (which is always low)

http://en.wikipedia.org/wiki/Autonomic_nervous_system

Wondering if I should force longer deeper breathing from the belly?

Try swimming, long slow breastroke helped with my breathing and I'm convinced it increased my lung capacity too...