OP,
Check out your gear and maybe get a lesson with someone else, but in all likelihood we only ever have ourselves to blame for our problems. I know this guy who studied with one of the best teachers in the world, developed all types of back problems, and got bitter about this teacher. He tried different studios and finally bought a new bow, focused on relaxation, and came out on the other side a bit embarrassed, but with a much more efficient and controlled technique... Unless there's some egregious issue with your teacher (like my old teacher who would throw pinecones at us when we'd mess up,) perhaps you should check your gear and videotape yourself a bit.
Finally... do you exercise at all? Getting some good cardio and hitting the floor at some quality yoga classes can work miracles for many of our tension issues.