Hello dear, I understand your concern.Though it started with fever and cough,but the way you are describing your left sided severe unilateral headache with excessive lacrimation and running nose,points to a very characteristic type of primary headache called cluster headache .But few points are against:your headache is persistent but cluster headache comes in clusters of short duration headache episodes.What appears to be upper respiratory tract infection(URTI) in your case can also otherwise be associated with headache,but not on one side, often.You need to visit your physician regarding this ,so that he may take a proper history and advise accordingly.I hope it helps.