Lumbar disc bulge and exercises?

Hi people

I am hoping you can chime in and recommend couple of exercises to ease my back pain? The MRI shows signs of dessication and L4-L5 disc bulge. I am terrified that it will rupture. 8 months ago, i abuse my back doing back handsprings and i havent done any core exercises except the Mckenzie extensions and the use of the lumbar roll. I used the roll extensively for months until the pain shifted to my thoracic back. In the meantime i didnt do any core strength exercises and right now, my back hurts everytime i run or bend over/down. I cant do much around and feel hopeless. Sitting in my cubicle for 8 hours doesnt help much. So i need your wise advice

- Sitting with correct posture (110 deg) but avoid sitting forward or straight (90 deg)
- Hyperextensions recently incorporated. Any other core strength ex?
- Stretches. This is where I am lacking of imagination.
- Pelvic tilt by my PT. But he was useless as he couldnt explain the proper form. He said to push down thus flatten the back. How do i do them? do i suck the stomach or do i push down. I am reading more and it looks like to suck your stomach and squeeze your buttocks tightly together
- Once i get the pelvic tilt, i can do ab crunches.

thanks