I'm a physiotherapist, and teach pole dancing and Pilates in my spare time. I've had an issue with a sore disc in my back for months and it comes and goes depending on what move I'm working on.
Generally flexing the back (sitting, lying on your back, bending, squatting, sit up's and inverting up) will make the buldge worse, and extensions (walking, standing tall, leaning back and 1/2 press ups's) will make it feel better. If not treated, it could start pinching on the nevers and causing lots and lots of pain.
I would suggest seeing a physical therapist – they will be able to asses your back, and also give you some specific treatment on getting core strength. It's all about the core and stabilising the lower back – not sit ups!! Learning to work your pelvic floor, and working on what we call a neutral spine has completly cured my back and I can do what ever I want on the pole. An example of some excellent core stabilisation techniques is demonstrated by KT coats (link below) getting you back to stay still while moving the legs
http://www.youtube.com/watch?v=lJZezT4T_MI
I can give you some other pilates type exercises to help as well…just give me a message!
Hope this helps!!