https://www.youtube.com/watch?v=NCtF9_DuzMU
https://www.youtube.com/user/GokhaleMethod?feature=watch
But be careful -- some of those positions can be hard on the back. Have you tried walking to start? Or swimming? Start gently, but often a bad back actually feels better when you move it as long as you don't strain.
Yes - easy beginner yoga can be very helpful. Go to Youtube and look there. You don't want advanced moves. I did just some very simple moves of lying on back, point toes down, hands at side, palms down, fingers straight. Slowly lift first one leg up to 90 degrees and then lower it. Do the same on the other side. The Indian guy teaching it said only do it once the first time if you are weak or having back pain. The next one was just as simple and easy. Look for ones like that.