hi
Thanks for your query
i can feel your concerns
i advise you to consult your doctor for clinical examination a
Normally cast result in abnormal sensations and burning pain.it ususually settle when 
fracture heal and cast is removed
loose cast after consulting your doctor
Move part which is out of cast 
i want to know adout your dietary habits
B12 deficiency also  presents with symptoms as your's
i advise you to take B12 and 
folic acid supplements after consulting your doctor.
improve your diet
avoid spicy and junk food
try to meat, fresh fruits and vegetables
i also advice to have your 
haemoglobin checked, 
take 
iron supplements after consulting your doctor
Hope i have ansewered your query
i am available for your help 
regards
Dr.imran