What causes limited neck movement along with severe lumbar and pelvic pain making walking or standing difficult?

Hi doctor,

I have bone bridging in my spine on the vertebrae which are fused together, and on my facet joints and also my sacroiliac joint. Going from the top, I have very limited movement in my neck with pinching sensations when I move my head. I have pain going down my right arm into my fingers, mostly the little finger. I have a loss of sensation in my thumb and index finger, and also weakness in my right arm. If I lay on my back both my arms from the back of my bicep to my fingers go numb. I have severe pain in my lumbar area and pelvis area going into my groin which sometimes can be so bad that I am unable to stand or walk. I get sharp pains in my buttock area down my legs which seem to be on the outer back part of my thigh down to my heel. I have had this problem since my early 20s. I have had an HLA B27 test done which was negative. My current medications include Naproxen, Duloxetine, Atorvastatin, Lansoprazole, Tamsulosin, Butec 5 mg, Transdermal patch, Testosterone replacement injection Nebido 4 ml. What could be the problem with my back? Please help.