Aso titre and headache after lumber punc

My son has been admitted in CMRI hospital Kolkata with fever, rash, headache and vomating since 17.12.18. after admission lots of test has been done as a result Aso titre 1500 with tonsillitis. After 04 days fever and rashes became normal but doctor could not identified where is the infection and made lumber puncture test before 06 days and a headache comes start after next day and control by the paracetamol but till date the pain become continuously without paracetamol.. Now doctor says it's a migraine pain and I doubt he want to divert their fault at the time of LP. Now suggest me how I know actual cause of the headache (it increased when he sit and standing position)? And how much days Aso  titre remaining high after decreased the fever?