I Am 66 Yr Old White Mail In Good Physical

I am 66 yr old white mail in good physical shape, blood work I'd good (all well within limits) but I have cramping in tendons in feet and legs. I have L4-L5 extruded disk with discogenic pain, peripheral neuropathy in both feet. Toes burn like 1st degree burn and there no feeling in the surface of toes. I don't have cramps during the day when I'm active, only at night when inactive. I have to get up and walk off the cramping. The doctor increased my Gabapentin to 600 mg at bedtime but it's not working. Any ideas?