Can you tell me why you believe the disc bulge isn't your source of pain?? Bulging discs are very commonly the source of low back pain. The bulge in the disc causes inflammmation and pressure on the structures around it therefore causing pain. The usual pattern of pain is referred to the buttock, hip and down the back of the thigh. If the bulge is large then pain can often be referred down below the knee.

Some useful reading/resources for you would be to look on the internet for the McKenzie Institute approach to back pain.

Can I ask how old you are and what caused your symptoms in the first place?? This may shed some light on what is going on. Also what activities make your pain worse??