http://www.spine-health.com/conditions/spine-anatomy/all-about-l4-l5-spinal-segment
I spent awhile reading and studying this and it might be good for you to do same. I have spinal stenosis beginning, as well as arthritic facets and some disk herniation going on. Right now I manage the pain but it can be debilitating and acute to where you cannot stand.
Helpful hint. Find the right way to sleep at night. A recliner seems to work best for me rather than a bed. It takes stres of my lower lumbar regions, starting at L4-L5 and S1, S2 As Gomer Pyle would say, I'm a mess. But you right now are worse.
You will need to have some serious discussions with the doc to move forward but, keep in mind they will want to try to do some therapy exercises that should hel strengthen that area and re-align those vertbral formations. Strengthening your CORE (ABS) is a must. They will almost require you to go through some of these things before agreeing to surgery... I had to the first time and nothing worked. But you have to try....
Surgery is LAST RESORT and even then there are no guarantees it will solve the problem...
SO, you need to get back up with the doc and make a plan as to how to proceed with getting you out of debillitationg pain from the disc disease, which also could possibly be herneated....