My back

I have lost about a pound since last week.  How I did it, I have no idea.  I am going to break the cycle of binging and giving up.  I have not and will not give up.  I have been having back pain lately and I would like to know the best exercises for a hurt back.  I went to the doctor yesterday and I found out that I have a degenerative condition that causes pain.  There was a curve of the spine and backbone.  I was told that my weight because of where it was stored played a role.  So, it was more than enough incentive for me to lose weight.  I have decided to exercise and diet, to do what is hard but it is hard because I allow it to be hard.  It is all in the mindset.  Walking sounds like a good exercise because it is so easy so I wonder what effect it will have on my back?  What are some good exercises for my back other than just stretches?  I will lose the weight and keep it off.  I plan to lose enough weight to get out of the 280+ lb. mark.