Hi welcome to HCm
Dear Vardhan , your problem  seems to be of 
anemia  suffering from neck pains and sleepiness is very common amongest todays generation due to their derailed  life style  and faulty food habits which lowers  immunity and  fall prey to different health problems .
I would like to suggest you to get yourself checked from a professional for anemia .
 In the  meanwhile  , Plan you meals . You need a well ballanced diet , including  essential nutrients , fiber ,
vitamins and minerals in natural form such as roasted meat & fish, Boiled eggs, skimmed milk & curd , beans and nuts  . Eat lot of green leafy and fresh fruit & vegetables
Drink plenty of water.  Lemon juice with water and honey twice a day and coconut water will give you instant energy .
Avoid processed foods carbs , sugar , fried ,fast foods , Tea , coffee ,alcohol and 
smoking , 
stress , 
sleeplessness and 
Constipation all will produce biochemical and metabolic conditions in your body that will decrease your immunity.
So avoiding is definitely the first step in the right direction to detoxing the body, boosting the immune system .
 For proper assimilation Along with well planned diet regimen , chalking out a well planned physical activity plan is also essential , to strengthen your immune system.
Stay erect while you stand ,sit or walk .Maintain right posture  to eliminate your neck or back  pain.
 Back bending Exercises ,  walking ,deep breathing , Kapalbatti , 
yoga - rolling , stretching , sit - ups and proper rest after work outs all help boost energy  &  strengthening immune system & help achieving  healthy body  . 
Regular follow up with your doctor is necessary
Hope this helps solve your query . Take care .All the best .
Dont hesitate to come back if have further query .