don't know if this is helpful or will even apply to your son but my nephew used to get ear infections all the time. his mom let him go to sleep all the time with a bottle of milk and once she stopped doing that the ear infections stopped. you said he is 4 so i doubt he still has a bottle but thought i'd mention it anyway. hope he gets better soon.
how to prevent ear infections in toddlers? . my 4 year old son keeps getting ear infections after a bout of cold. he has been on antibiotics every month for the past 3-4 months.