medically unreliable = disabled??

As I have stated before I suffer from a spinal issue called Spondylolisthesis I also suffer from frequent Migraine headaches. Oftentimes I am unable to report for work or if I can go to work I am not at my full capacity and not able to function to preform all of my duties. It was suggested (by a medical provider) that my unreliability may make it difficult to stay gainfully employed and have I considered applying for SSDI? This was last week that she suggested this and now I can't stop thinking about it. I am afraid to become a "welfare case" again, I grew-up that way and don't want to go back to that life.

However she has a good point, if I were my employer I would not keep me on staff because you just never know when I am going to call out or show up unable to pull my weight. So I am torn, I don't know what to do. Part of the reason I am so up in the air on this is that, I do know that at some point in the not to distant future I am going to have to have an operation for by back that will lay me up for anywhere from 6 weeks to 6 months!! How do I survive during that time?

Here are some MRI images the left is mine and the right is a normal spine. Note the L5 S1 area (which I have marked) see the difference between the two??

On mine the L5 juts to the left on the normal it is in a nice line. Also the form is badly compromised on mine, those two vertabra are totally different shapes than the ones above them or in the normal image.