Lower back pain

I have severe lower back and left leg pain that radiates down to the sole of my foot. The pain in my leg feels like a constant lightning bolt or an electric shock accompanied by muscle spasms and numbness, while the sole of my foot experiences a pressing, compressive pain that worsens when applying pressure, sitting, or leaning on my foot. All of these symptoms worsen significantly with walking for a distance, lifting things, or even engaging in light exercise.

Recently, I attended a physical therapy center where they recommended specific exercises. Despite their simplicity, these exercises drastically increased the intensity of my pain, causing it to extend up to my mid-back.

The full X-rays of my back, as well as the MRI of the lumbar spine, do not show any obvious problems. I have been suffering severely for a year now; I cannot walk for more than ten minutes, I cannot sit in certain positions, and I am unable to sleep most of the time due to the intense pain. The problem is that yesterday, the pain started spreading to my right leg, and now I walk with extreme difficulty. I do not want a diagnosis, but what are the possible potential causes? Which specialist should I consult, keeping in mind that I have seen three neurologists, and they all agreed that there is no obvious cause?"