I now do an hour of yoga every morning, which is basically a mixture of breathing exercises and stretching. Keep it simple, look up a couple of basic youtube videos or better still hire someone to teach you the basics. It takes a while to build up the will to do it every morning, but once you've got the basics down your back will thank you.
I use to go swim every other day, but that's been on hold these past couple of months. best of luck.
Also recommend the Yoga 'pigeon' pose.
Anything that improves your core strength should help I've been told.