Obvious question is obvious, but may also be helpful: have you seen a competent psychotherapist?
If the tension is indeed psychosomatic, then treating the psychological cause may be the way to go.
Other things that would be worth investigating: Alexander Technique, Pilates (yes, seriously. What you're describing could be breathing-related in particular, and Pilates is good at that stuff. Go for a teacher accredited by an organisation with a multi-year training program.), Tension Mytosis Syndrome, T'ai Chi (again, seriously. Good t'ai chi can be very useful), trigger point therapy (read http://www.amazon.com/Trigger-Point-Therapy-Workbook-Self-Tr...), deep tissue massage (painful but effective).
If the tension is indeed psychosomatic, then treating the psychological cause may be the way to go.
Other things that would be worth investigating: Alexander Technique, Pilates (yes, seriously. What you're describing could be breathing-related in particular, and Pilates is good at that stuff. Go for a teacher accredited by an organisation with a multi-year training program.), Tension Mytosis Syndrome, T'ai Chi (again, seriously. Good t'ai chi can be very useful), trigger point therapy (read http://www.amazon.com/Trigger-Point-Therapy-Workbook-Self-Tr...), deep tissue massage (painful but effective).