Well your foot doc will probably recommend you to a neurologist .And theres a lot of different scans, the MRI one is the one where they put you in the tube for 20 minutes and takes an image of your back and spainal cord to ascertain whether you have pinched nerves, or if a disc is out of whack{sometimes all it takes is a teensy millimeter to cause excruciating pain.}
Then there are tests where they insert small needles here and there on varios parts of your feet and legs to give you a very tiny shock in order to measure your nervees respponse. Its uncomfortable, but not bad, and honestly nothing like the pain you live with.
All this of course is to rule out IF its a back problem, in which case you deal with it...maybe meds, maybe physical therapy, maybe surgery{last resort}
If Its NOT a back problem, well, the search goes on.
Neurapathy is a miserable uncertain thing to deal with, and So many factors affect the out come, the causes,age ,weight, sex, genes, lifestyle, mindset, and to an extent, finances....sometimes people have to be able to afford to stay home from work awhile before they get better. Lets hope you get better soon.
If possible, rule out causes, itentify causes, fix causes....and then work on growing back those nerves!!!
Do discuss the gabapentun with your doc, its one of the better options in a pretty sparse field.