Neck and Shoulder Injuries

I swam competitively from age 9 through high school and hated it. Now at age 30, I joined a local Master's team and love it. My friends say that it is my religion. My change of heart is a different topic however. Now I need some help solving my latest "possible" swimming related problem. I read another post about cervical injury and swimming but thought that this was a somewhat different subject. Over the past three months, I have had numerous whiplash injuries to my neck and shoulders. Both my right and left sides have been affected. I end up in the doctor's office in such pain that I need muscle relaxants, vicodin, a whole lot of icy hot and some beer to move about. I end up taking time off of swimming to let my injuries heal. The doctors think that it might be swimming related. I personally don't think so and don't want it to be (since I now love it). But maybe I am doing something inadvertently. 1) I have been told that I have "beautiful" stroke technique (expect backstroke where I cross over) 2) I never dive in except in meets 3) I alternate breathe except when my neck won't allow it 4) The pool is over 80 degrees 5) I swim three to four times a week 3500 yards at a time I want to know if anyone else has these problems or if anyone can think of swimming related techniques that would cause this. Thanks