Pilates was definitely the answer for me. It was recommended to me by my oseopath and I found a small class with a great teacher who really understands back problems. I have a very curved lower back too and the pilates has really helped. Find a small class if you can so that the instructor can keep a check on your posture - you don't want to make it worse! I used to find I was particularly stiff when I got out of bed - my osteopath suggested putting a pillow under my knees when laying on my back and between my knees when laying on my side, plus, give your knees a good hug before you get out of bed.