I have been noticing more and more lately that I really clamp down with my fretting hand, putting a lot of pressure with my thumb on the back of the neck and in turn really wearing out my hand/arm fast.

I don't really know how to correct this and it is affecting my playing ability because any thing that is somewhat repetitive causes my arm to ache.

I saw a blues duo play last night and the bass player was very seasoned and because of this made it look like his bass was lighter then air and almost playing itself. He was really loose with both his fretting hand and striking hand but still had great tone.

Below is a picture of my usual playing position.

Please help!

http://i80.photobucket.com/albums/j170/Jeff_erson/bassstance.jpg