My 3 Month Old Dd Diagonised With An Ear Infection..

My 3 month old dd diagonised with an ear infection.. she is taking anti biotic.. how can i protect her from ear infection.. many are saying that if she gets ear infection once then this will get repeated often is that true?.. i fed her in lying down position and i have force letdown is that the reason for her ear infection?.. now i am feeding her with her head elevated to 45 degree but sometimes she coughs in the middle will that make the milk to enter her eustachian tube.. please advise