I have suffered from very painfull back (pain measurement of 7-10) and this all started when doctors diagnosed guillain-barre. Lastpainlessday13mtago?
Second opinion. Guillain barre usually not painful; can be after infection, etc. Could be muscular, fracture, bone abnormality (even cancer of, or spread to bone-don't know your age, sex, history). May need tests like xray, mri, ct, phys. Therapy, oral meds, local injections... Or not. May need exam by physiatrist (physical med), rheum, (med specialist in joints), ortho, neurology, can't tell here. See your doc.