middle and upper back pain, need exercises for in a chair

I was in an accident which caused great pain to my middle and upper back as well as my neck. I am seeing a chiropractor but after only two visits I am not hopeful for longer lasting back health. feeling better from the visits seem to last just a few hours. I sit in a chair all day and often have to lay down because of the back pain which comes back. I was wondering if anyone could describe to me some very good exercises for someone in my position that can be done from a chair. I've googled and looked for exercises and either their descriptions are inadequate or the photos don't tell you how to do the exercise from start to finish. i would really appreciate any help anyone can offer i'm in pain here.