Based on your symptoms, i would lean towards
magnesium deficiency (stress is also a major cause of
magnesium deficiency). Both magnesium and vitamin B12 deficiencies symptoms include tremors, fatigue, back pain (magnesium lists neck pain as well), itching, dizziness, concentration problems (brain fog), tingling/numbness, muscle weakness. Both are also easily misdiagnosed.....
"Why is B12 deficiency so under-diagnosed?
B12 deficiency is often missed for two reasons.