My vitamin D is very low and I am feeling malaise. What to do?

Hi doctor,

I am a 21-year-old final-year student. I started feeling malaise after four weeks associated with fatigue. I thought it was a subclinical viral infection and took bed rest. Slowly my limbs started to pain. However, I had pain only in my thighs. It gradually progressed over two weeks, and now I cannot walk for 50 feet or stand for more than three minutes without resting my thigh. The pain gets relieved on resting, but soon twitching starts all over the legs and face. This pain is aching in type and is severe. I had a complete hemogram, liver function test, thyroid profile, ECG, serum electrolytes, calcium, phosphorus, creatinine phosphokinase, B6, folic acid, and nerve conduction study. All were normal except vitamin D, which is very low at 14 ng/dL. I have been diagnosed with OCD, and I have been taking Escitalopram for the past two years and Fluvoxamine and Clofranil for three years before that. I am taking Felicita once in the afternoon, Clonazepam 0.25 mg thrice daily, and Escitalopram once daily. My thigh pain is too much. Please help me.