HELP''; HE IS ALWAYS DEMANDING FOR ORAL SEX

My name is Rita, A graduate from one of Nigeria"s prestigious institution; I am in a 5 years old relationship which is eventually going to end up in marriage soonest But am stuck in the middle of nowhere: Daniel has been instrumental in my educational pursuit to the level i have attained today.        The thing is this, four out of the five years we have been relating, sex was struck out through a mutual understanding. But since we started a sexual relationship, though its been exciting but he is always asking for the oral thing you know what that mean.                                                                                     Well i let him have his way on few occasion but its becoming unbecoming and am getting fed up and he is not giving it up. plus, this has slowed down preparations towards our Union.                            Please help with advise on what to do. I love him and i dont want to loose him. Am open minded.