What to do about work?

I'm the kinda guy that really hates to let people down.  I think that's the reason that I haven't gone and done something already that I need to do.  I need to file for disability, but I don't want to let my boss at work down by quitting.

Things with my back have become really painful, and the only times that they aren't painful are when I'm so drugged up that I cannot even think.  I knew it was going to be rough working here because of my back situation, but I didn't expect it to get worse over time.  I really believe that working is causing the problem too.  Now, on top of the back thing, I have this new thing going on in my right foot that is making it difficult to walk as well.  It's a pain that runs down my leg, around my ankle, and then finishes with my heel, causing such pain that I don't even want to stand on it anymore.  I asked my doctor if this could be related to my diabetes, but he couldn't be sure.  He said that it was most likely related to my back issues.  I hope not.

I wish that there was someone that could tell me what to do, as I have no idea how to proceed.  I know that if I continue working that it's only going to get worse, but I so want to keep doing a good job for my bosses.  I would really miss this place I think.  

This is so frustrating...sigh...