Backpain that limits activity.?

I had a back injury whyle serving in the military, 1 surgery and several years later, i want to get back into shape, but any strenous activity will send me int a week of pain, headaches, and general moodieness, i hate it, i have pain pills to take, but dont unless i really have to, worried about getting adicted, also, take muscle relaxers and nsaids, I dont want to be fat forever, i want to do the things i used to, like run and lift and boat, hike, its depressing to me that ...the tought of having to be this way...forever, im not 40 yet, i feel like 80.