For a long-term solution, build up the core muscles in your body. I find yoga very good for my bulging disc.

Short-term - try lying on your back on the floor (make sure you have something sturdy to pull yourself up with nearby) and then bring your knees to your chest. Grab hold of your legs behind the knees, and start rocking gently on your back. This will help straighten out your back.

Short term #2 - still on the floor, lie on your tummy, and push yourself up onto your elbows. Keep your hips on the floor, and your shoulders down (don't let them hunch up). Stay like this for about 15mins if you can. Once that's an easy exercise (usually a couple of weeks at least) then do it daily for 5 mins at a hit.

But in all seriousness, go to a physio for proper exercises. These ones should give you some short-term relief.