I also have had problems for many years at L4-5 also S1 I too had a discectomy I lived for 20 something years with a ruptured disk at L4-5 then I finally couldn't take the pain anymore.

Had my first surgery in 2009 took me about 6 months total to get back to what I considered good enough to go back to work.

Long story short I had a so called redo of L4-5 again in 2011 due to a injury from falling from the top step of my tractor trailer.

Since then I have not been normal I live with pain such as you with my left leg feeling like it is a dead weight some day are better than others.Some days I have sharp shooting pains from lower lumbar all the way down to my toes. Done the meds for many years now.
Pain management doc suggested a scs device because I'm not a surgical candidate anymore seeing I never recovered fully from my last surgery.

Couple of weeks ago my surgeon that is going to do the trail for the scs labeled my problem Failed back syndrome (My trial is the 23rd of this month.) Hopefully it will bring a lot of relief for me.

So my suggestion is as Dr.Smith said I would do some reasearch and see if you fit into any of the categories of F.B.S.

I really hope you can find some answers soon and relief also.
Remember we all are here and are glad you found us hopefully some of the veterans here can help you a little more in your quest for answers and guidance in the right direction.

I know they have been so helpful with me