HI I have gone through your mail,as you said your son is having cough,congestion fever and ear pain
right side later he noticed watery fluid is leaking from his left ear and this drained fluid is forming a crust at external ear canal
after drying, considering your all these complaints I am suspecting that your son is having upper respiratory tract
infection with acute otitis media
both ears,please need not to worry,at first your son was having nasal congestion
and nasal dischage which had spread posteriorly to involve the throat thus producing the cough, after this infection had spread further via eustechian tube (tubular connection between throat and ear)to his both ears to developed disease called as acute otitis
media in both ears,on right ear this is giving pain only while on left ear probably it had developed small hole in ear drum which causes leaking of accumulated fluid in ear canal. My opinion is that you should contact your E.N.T.specialist for clinical examination of nose,throat and ears of your son,you are also adviced to go for these basic investigations like-(1) C.T.Scan of paranasal sinuses
,(2) Culture & sensitivity of nasal discharge and throat swab,(3) pure tone audiometery of ears,(4) Impedance audiometery of both ears,(5) Blood-CBC, ESR, Sugar (fasting & PP ).After findings of physical eamination by your doctor and co-relating them with results of investigations one can make correct diagnosis than only treatment may be planed in right direction.Thanks.