Good Morning,
Sorry to hear about the pain you are suffering from.
The bones of the back/ spine, are adjacent to the Lumbar Plexus of Nerves.When you have a Prolapsed Disc or
spondylolisthesis that has been diagnosed and treated, it a common complication to have compression symptoms of these nerves, that lead to
numbness / dragging type of pain of the legs.
If symtoms are tolerable and occur once or twice in a week, I would recommend you to undergo
physiotherapy with Lumbar Traction and IFT and take an oral dose of vit.B12,( which I am sure you are already taking;Methylcobalamine).The symptoms will relieve slowly.
On the other hand if the numbness and pain are severe and not tolerable, you may require a surgery to decompress the the nerve.
Kindly consult a nuerosurgeon for the same.
Hope you pain starts decreasing soon.
Good luck mate !